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authorIngo Molnar <mingo@elte.hu>2009-09-07 08:19:51 +0200
committerIngo Molnar <mingo@elte.hu>2009-09-07 08:19:51 +0200
commita1922ed661ab2c1637d0b10cde933bd9cd33d965 (patch)
tree0f1777542b385ebefd30b3586d830fd8ed6fda5b /arch/x86/lguest/boot.c
parent75e33751ca8bbb72dd6f1a74d2810ddc8cbe4bdf (diff)
parentd28daf923ac5e4a0d7cecebae56f3e339189366b (diff)
downloadlinux-2.6.38-lt-ux500-a1922ed661ab2c1637d0b10cde933bd9cd33d965.tar.gz
Merge branch 'tracing/core' into tracing/hw-breakpoints
Conflicts: arch/Kconfig kernel/trace/trace.h Merge reason: resolve the conflicts, plus adopt to the new ring-buffer APIs. Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/x86/lguest/boot.c')
-rw-r--r--arch/x86/lguest/boot.c510
1 files changed, 350 insertions, 160 deletions
diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c
index 7bc65f0f62c..d677fa9ca65 100644
--- a/arch/x86/lguest/boot.c
+++ b/arch/x86/lguest/boot.c
@@ -22,7 +22,8 @@
*
* So how does the kernel know it's a Guest? We'll see that later, but let's
* just say that we end up here where we replace the native functions various
- * "paravirt" structures with our Guest versions, then boot like normal. :*/
+ * "paravirt" structures with our Guest versions, then boot like normal.
+:*/
/*
* Copyright (C) 2006, Rusty Russell <rusty@rustcorp.com.au> IBM Corporation.
@@ -74,7 +75,8 @@
*
* The Guest in our tale is a simple creature: identical to the Host but
* behaving in simplified but equivalent ways. In particular, the Guest is the
- * same kernel as the Host (or at least, built from the same source code). :*/
+ * same kernel as the Host (or at least, built from the same source code).
+:*/
struct lguest_data lguest_data = {
.hcall_status = { [0 ... LHCALL_RING_SIZE-1] = 0xFF },
@@ -85,7 +87,8 @@ struct lguest_data lguest_data = {
.syscall_vec = SYSCALL_VECTOR,
};
-/*G:037 async_hcall() is pretty simple: I'm quite proud of it really. We have a
+/*G:037
+ * async_hcall() is pretty simple: I'm quite proud of it really. We have a
* ring buffer of stored hypercalls which the Host will run though next time we
* do a normal hypercall. Each entry in the ring has 5 slots for the hypercall
* arguments, and a "hcall_status" word which is 0 if the call is ready to go,
@@ -94,7 +97,8 @@ struct lguest_data lguest_data = {
* If we come around to a slot which hasn't been finished, then the table is
* full and we just make the hypercall directly. This has the nice side
* effect of causing the Host to run all the stored calls in the ring buffer
- * which empties it for next time! */
+ * which empties it for next time!
+ */
static void async_hcall(unsigned long call, unsigned long arg1,
unsigned long arg2, unsigned long arg3,
unsigned long arg4)
@@ -103,9 +107,11 @@ static void async_hcall(unsigned long call, unsigned long arg1,
static unsigned int next_call;
unsigned long flags;
- /* Disable interrupts if not already disabled: we don't want an
+ /*
+ * Disable interrupts if not already disabled: we don't want an
* interrupt handler making a hypercall while we're already doing
- * one! */
+ * one!
+ */
local_irq_save(flags);
if (lguest_data.hcall_status[next_call] != 0xFF) {
/* Table full, so do normal hcall which will flush table. */
@@ -125,8 +131,9 @@ static void async_hcall(unsigned long call, unsigned long arg1,
local_irq_restore(flags);
}
-/*G:035 Notice the lazy_hcall() above, rather than hcall(). This is our first
- * real optimization trick!
+/*G:035
+ * Notice the lazy_hcall() above, rather than hcall(). This is our first real
+ * optimization trick!
*
* When lazy_mode is set, it means we're allowed to defer all hypercalls and do
* them as a batch when lazy_mode is eventually turned off. Because hypercalls
@@ -136,7 +143,8 @@ static void async_hcall(unsigned long call, unsigned long arg1,
* lguest_leave_lazy_mode().
*
* So, when we're in lazy mode, we call async_hcall() to store the call for
- * future processing: */
+ * future processing:
+ */
static void lazy_hcall1(unsigned long call,
unsigned long arg1)
{
@@ -146,6 +154,7 @@ static void lazy_hcall1(unsigned long call,
async_hcall(call, arg1, 0, 0, 0);
}
+/* You can imagine what lazy_hcall2, 3 and 4 look like. :*/
static void lazy_hcall2(unsigned long call,
unsigned long arg1,
unsigned long arg2)
@@ -181,8 +190,10 @@ static void lazy_hcall4(unsigned long call,
}
#endif
-/* When lazy mode is turned off reset the per-cpu lazy mode variable and then
- * issue the do-nothing hypercall to flush any stored calls. */
+/*G:036
+ * When lazy mode is turned off reset the per-cpu lazy mode variable and then
+ * issue the do-nothing hypercall to flush any stored calls.
+:*/
static void lguest_leave_lazy_mmu_mode(void)
{
kvm_hypercall0(LHCALL_FLUSH_ASYNC);
@@ -208,9 +219,11 @@ static void lguest_end_context_switch(struct task_struct *next)
* check there before it tries to deliver an interrupt.
*/
-/* save_flags() is expected to return the processor state (ie. "flags"). The
+/*
+ * save_flags() is expected to return the processor state (ie. "flags"). The
* flags word contains all kind of stuff, but in practice Linux only cares
- * about the interrupt flag. Our "save_flags()" just returns that. */
+ * about the interrupt flag. Our "save_flags()" just returns that.
+ */
static unsigned long save_fl(void)
{
return lguest_data.irq_enabled;
@@ -222,13 +235,15 @@ static void irq_disable(void)
lguest_data.irq_enabled = 0;
}
-/* Let's pause a moment. Remember how I said these are called so often?
+/*
+ * Let's pause a moment. Remember how I said these are called so often?
* Jeremy Fitzhardinge optimized them so hard early in 2009 that he had to
* break some rules. In particular, these functions are assumed to save their
* own registers if they need to: normal C functions assume they can trash the
* eax register. To use normal C functions, we use
* PV_CALLEE_SAVE_REGS_THUNK(), which pushes %eax onto the stack, calls the
- * C function, then restores it. */
+ * C function, then restores it.
+ */
PV_CALLEE_SAVE_REGS_THUNK(save_fl);
PV_CALLEE_SAVE_REGS_THUNK(irq_disable);
/*:*/
@@ -237,18 +252,18 @@ PV_CALLEE_SAVE_REGS_THUNK(irq_disable);
extern void lg_irq_enable(void);
extern void lg_restore_fl(unsigned long flags);
-/*M:003 Note that we don't check for outstanding interrupts when we re-enable
- * them (or when we unmask an interrupt). This seems to work for the moment,
- * since interrupts are rare and we'll just get the interrupt on the next timer
- * tick, but now we can run with CONFIG_NO_HZ, we should revisit this. One way
- * would be to put the "irq_enabled" field in a page by itself, and have the
- * Host write-protect it when an interrupt comes in when irqs are disabled.
- * There will then be a page fault as soon as interrupts are re-enabled.
+/*M:003
+ * We could be more efficient in our checking of outstanding interrupts, rather
+ * than using a branch. One way would be to put the "irq_enabled" field in a
+ * page by itself, and have the Host write-protect it when an interrupt comes
+ * in when irqs are disabled. There will then be a page fault as soon as
+ * interrupts are re-enabled.
*
* A better method is to implement soft interrupt disable generally for x86:
* instead of disabling interrupts, we set a flag. If an interrupt does come
* in, we then disable them for real. This is uncommon, so we could simply use
- * a hypercall for interrupt control and not worry about efficiency. :*/
+ * a hypercall for interrupt control and not worry about efficiency.
+:*/
/*G:034
* The Interrupt Descriptor Table (IDT).
@@ -261,10 +276,12 @@ extern void lg_restore_fl(unsigned long flags);
static void lguest_write_idt_entry(gate_desc *dt,
int entrynum, const gate_desc *g)
{
- /* The gate_desc structure is 8 bytes long: we hand it to the Host in
+ /*
+ * The gate_desc structure is 8 bytes long: we hand it to the Host in
* two 32-bit chunks. The whole 32-bit kernel used to hand descriptors
* around like this; typesafety wasn't a big concern in Linux's early
- * years. */
+ * years.
+ */
u32 *desc = (u32 *)g;
/* Keep the local copy up to date. */
native_write_idt_entry(dt, entrynum, g);
@@ -272,9 +289,11 @@ static void lguest_write_idt_entry(gate_desc *dt,
kvm_hypercall3(LHCALL_LOAD_IDT_ENTRY, entrynum, desc[0], desc[1]);
}
-/* Changing to a different IDT is very rare: we keep the IDT up-to-date every
+/*
+ * Changing to a different IDT is very rare: we keep the IDT up-to-date every
* time it is written, so we can simply loop through all entries and tell the
- * Host about them. */
+ * Host about them.
+ */
static void lguest_load_idt(const struct desc_ptr *desc)
{
unsigned int i;
@@ -305,9 +324,11 @@ static void lguest_load_gdt(const struct desc_ptr *desc)
kvm_hypercall3(LHCALL_LOAD_GDT_ENTRY, i, gdt[i].a, gdt[i].b);
}
-/* For a single GDT entry which changes, we do the lazy thing: alter our GDT,
+/*
+ * For a single GDT entry which changes, we do the lazy thing: alter our GDT,
* then tell the Host to reload the entire thing. This operation is so rare
- * that this naive implementation is reasonable. */
+ * that this naive implementation is reasonable.
+ */
static void lguest_write_gdt_entry(struct desc_struct *dt, int entrynum,
const void *desc, int type)
{
@@ -317,29 +338,36 @@ static void lguest_write_gdt_entry(struct desc_struct *dt, int entrynum,
dt[entrynum].a, dt[entrynum].b);
}
-/* OK, I lied. There are three "thread local storage" GDT entries which change
+/*
+ * OK, I lied. There are three "thread local storage" GDT entries which change
* on every context switch (these three entries are how glibc implements
- * __thread variables). So we have a hypercall specifically for this case. */
+ * __thread variables). So we have a hypercall specifically for this case.
+ */
static void lguest_load_tls(struct thread_struct *t, unsigned int cpu)
{
- /* There's one problem which normal hardware doesn't have: the Host
+ /*
+ * There's one problem which normal hardware doesn't have: the Host
* can't handle us removing entries we're currently using. So we clear
- * the GS register here: if it's needed it'll be reloaded anyway. */
+ * the GS register here: if it's needed it'll be reloaded anyway.
+ */
lazy_load_gs(0);
lazy_hcall2(LHCALL_LOAD_TLS, __pa(&t->tls_array), cpu);
}
-/*G:038 That's enough excitement for now, back to ploughing through each of
- * the different pv_ops structures (we're about 1/3 of the way through).
+/*G:038
+ * That's enough excitement for now, back to ploughing through each of the
+ * different pv_ops structures (we're about 1/3 of the way through).
*
* This is the Local Descriptor Table, another weird Intel thingy. Linux only
* uses this for some strange applications like Wine. We don't do anything
- * here, so they'll get an informative and friendly Segmentation Fault. */
+ * here, so they'll get an informative and friendly Segmentation Fault.
+ */
static void lguest_set_ldt(const void *addr, unsigned entries)
{
}
-/* This loads a GDT entry into the "Task Register": that entry points to a
+/*
+ * This loads a GDT entry into the "Task Register": that entry points to a
* structure called the Task State Segment. Some comments scattered though the
* kernel code indicate that this used for task switching in ages past, along
* with blood sacrifice and astrology.
@@ -347,19 +375,21 @@ static void lguest_set_ldt(const void *addr, unsigned entries)
* Now there's nothing interesting in here that we don't get told elsewhere.
* But the native version uses the "ltr" instruction, which makes the Host
* complain to the Guest about a Segmentation Fault and it'll oops. So we
- * override the native version with a do-nothing version. */
+ * override the native version with a do-nothing version.
+ */
static void lguest_load_tr_desc(void)
{
}
-/* The "cpuid" instruction is a way of querying both the CPU identity
+/*
+ * The "cpuid" instruction is a way of querying both the CPU identity
* (manufacturer, model, etc) and its features. It was introduced before the
* Pentium in 1993 and keeps getting extended by both Intel, AMD and others.
* As you might imagine, after a decade and a half this treatment, it is now a
* giant ball of hair. Its entry in the current Intel manual runs to 28 pages.
*
* This instruction even it has its own Wikipedia entry. The Wikipedia entry
- * has been translated into 4 languages. I am not making this up!
+ * has been translated into 5 languages. I am not making this up!
*
* We could get funky here and identify ourselves as "GenuineLguest", but
* instead we just use the real "cpuid" instruction. Then I pretty much turned
@@ -371,7 +401,8 @@ static void lguest_load_tr_desc(void)
* Replacing the cpuid so we can turn features off is great for the kernel, but
* anyone (including userspace) can just use the raw "cpuid" instruction and
* the Host won't even notice since it isn't privileged. So we try not to get
- * too worked up about it. */
+ * too worked up about it.
+ */
static void lguest_cpuid(unsigned int *ax, unsigned int *bx,
unsigned int *cx, unsigned int *dx)
{
@@ -379,38 +410,63 @@ static void lguest_cpuid(unsigned int *ax, unsigned int *bx,
native_cpuid(ax, bx, cx, dx);
switch (function) {
- case 1: /* Basic feature request. */
- /* We only allow kernel to see SSE3, CMPXCHG16B and SSSE3 */
+ /*
+ * CPUID 0 gives the highest legal CPUID number (and the ID string).
+ * We futureproof our code a little by sticking to known CPUID values.
+ */
+ case 0:
+ if (*ax > 5)
+ *ax = 5;
+ break;
+
+ /*
+ * CPUID 1 is a basic feature request.
+ *
+ * CX: we only allow kernel to see SSE3, CMPXCHG16B and SSSE3
+ * DX: SSE, SSE2, FXSR, MMX, CMOV, CMPXCHG8B, TSC, FPU and PAE.
+ */
+ case 1:
*cx &= 0x00002201;
- /* SSE, SSE2, FXSR, MMX, CMOV, CMPXCHG8B, TSC, FPU, PAE. */
*dx &= 0x07808151;
- /* The Host can do a nice optimization if it knows that the
+ /*
+ * The Host can do a nice optimization if it knows that the
* kernel mappings (addresses above 0xC0000000 or whatever
* PAGE_OFFSET is set to) haven't changed. But Linux calls
* flush_tlb_user() for both user and kernel mappings unless
- * the Page Global Enable (PGE) feature bit is set. */
+ * the Page Global Enable (PGE) feature bit is set.
+ */
*dx |= 0x00002000;
- /* We also lie, and say we're family id 5. 6 or greater
+ /*
+ * We also lie, and say we're family id 5. 6 or greater
* leads to a rdmsr in early_init_intel which we can't handle.
- * Family ID is returned as bits 8-12 in ax. */
+ * Family ID is returned as bits 8-12 in ax.
+ */
*ax &= 0xFFFFF0FF;
*ax |= 0x00000500;
break;
+ /*
+ * 0x80000000 returns the highest Extended Function, so we futureproof
+ * like we do above by limiting it to known fields.
+ */
case 0x80000000:
- /* Futureproof this a little: if they ask how much extended
- * processor information there is, limit it to known fields. */
if (*ax > 0x80000008)
*ax = 0x80000008;
break;
+
+ /*
+ * PAE systems can mark pages as non-executable. Linux calls this the
+ * NX bit. Intel calls it XD (eXecute Disable), AMD EVP (Enhanced
+ * Virus Protection). We just switch turn if off here, since we don't
+ * support it.
+ */
case 0x80000001:
- /* Here we should fix nx cap depending on host. */
- /* For this version of PAE, we just clear NX bit. */
*dx &= ~(1 << 20);
break;
}
}
-/* Intel has four control registers, imaginatively named cr0, cr2, cr3 and cr4.
+/*
+ * Intel has four control registers, imaginatively named cr0, cr2, cr3 and cr4.
* I assume there's a cr1, but it hasn't bothered us yet, so we'll not bother
* it. The Host needs to know when the Guest wants to change them, so we have
* a whole series of functions like read_cr0() and write_cr0().
@@ -425,7 +481,8 @@ static void lguest_cpuid(unsigned int *ax, unsigned int *bx,
* name like "FPUTRAP bit" be a little less cryptic?
*
* We store cr0 locally because the Host never changes it. The Guest sometimes
- * wants to read it and we'd prefer not to bother the Host unnecessarily. */
+ * wants to read it and we'd prefer not to bother the Host unnecessarily.
+ */
static unsigned long current_cr0;
static void lguest_write_cr0(unsigned long val)
{
@@ -438,18 +495,22 @@ static unsigned long lguest_read_cr0(void)
return current_cr0;
}
-/* Intel provided a special instruction to clear the TS bit for people too cool
+/*
+ * Intel provided a special instruction to clear the TS bit for people too cool
* to use write_cr0() to do it. This "clts" instruction is faster, because all
- * the vowels have been optimized out. */
+ * the vowels have been optimized out.
+ */
static void lguest_clts(void)
{
lazy_hcall1(LHCALL_TS, 0);
current_cr0 &= ~X86_CR0_TS;
}
-/* cr2 is the virtual address of the last page fault, which the Guest only ever
+/*
+ * cr2 is the virtual address of the last page fault, which the Guest only ever
* reads. The Host kindly writes this into our "struct lguest_data", so we
- * just read it out of there. */
+ * just read it out of there.
+ */
static unsigned long lguest_read_cr2(void)
{
return lguest_data.cr2;
@@ -458,10 +519,12 @@ static unsigned long lguest_read_cr2(void)
/* See lguest_set_pte() below. */
static bool cr3_changed = false;
-/* cr3 is the current toplevel pagetable page: the principle is the same as
+/*
+ * cr3 is the current toplevel pagetable page: the principle is the same as
* cr0. Keep a local copy, and tell the Host when it changes. The only
* difference is that our local copy is in lguest_data because the Host needs
- * to set it upon our initial hypercall. */
+ * to set it upon our initial hypercall.
+ */
static void lguest_write_cr3(unsigned long cr3)
{
lguest_data.pgdir = cr3;
@@ -506,7 +569,7 @@ static void lguest_write_cr4(unsigned long val)
* cr3 ---> +---------+
* | --------->+---------+
* | | | PADDR1 |
- * Top-level | | PADDR2 |
+ * Mid-level | | PADDR2 |
* (PMD) page | | |
* | | Lower-level |
* | | (PTE) page |
@@ -526,21 +589,62 @@ static void lguest_write_cr4(unsigned long val)
* Index into top Index into second Offset within page
* page directory page pagetable page
*
- * The kernel spends a lot of time changing both the top-level page directory
- * and lower-level pagetable pages. The Guest doesn't know physical addresses,
- * so while it maintains these page tables exactly like normal, it also needs
- * to keep the Host informed whenever it makes a change: the Host will create
- * the real page tables based on the Guests'.
+ * Now, unfortunately, this isn't the whole story: Intel added Physical Address
+ * Extension (PAE) to allow 32 bit systems to use 64GB of memory (ie. 36 bits).
+ * These are held in 64-bit page table entries, so we can now only fit 512
+ * entries in a page, and the neat three-level tree breaks down.
+ *
+ * The result is a four level page table:
+ *
+ * cr3 --> [ 4 Upper ]
+ * [ Level ]
+ * [ Entries ]
+ * [(PUD Page)]---> +---------+
+ * | --------->+---------+
+ * | | | PADDR1 |
+ * Mid-level | | PADDR2 |
+ * (PMD) page | | |
+ * | | Lower-level |
+ * | | (PTE) page |
+ * | | | |
+ * .... ....
+ *
+ *
+ * And the virtual address is decoded as:
+ *
+ * 1 1 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
+ * |<-2->|<--- 9 bits ---->|<---- 9 bits --->|<------ 12 bits ------>|
+ * Index into Index into mid Index into lower Offset within page
+ * top entries directory page pagetable page
+ *
+ * It's too hard to switch between these two formats at runtime, so Linux only
+ * supports one or the other depending on whether CONFIG_X86_PAE is set. Many
+ * distributions turn it on, and not just for people with silly amounts of
+ * memory: the larger PTE entries allow room for the NX bit, which lets the
+ * kernel disable execution of pages and increase security.
+ *
+ * This was a problem for lguest, which couldn't run on these distributions;
+ * then Matias Zabaljauregui figured it all out and implemented it, and only a
+ * handful of puppies were crushed in the process!
+ *
+ * Back to our point: the kernel spends a lot of time changing both the
+ * top-level page directory and lower-level pagetable pages. The Guest doesn't
+ * know physical addresses, so while it maintains these page tables exactly
+ * like normal, it also needs to keep the Host informed whenever it makes a
+ * change: the Host will create the real page tables based on the Guests'.
*/
-/* The Guest calls this to set a second-level entry (pte), ie. to map a page
- * into a process' address space. We set the entry then tell the Host the
- * toplevel and address this corresponds to. The Guest uses one pagetable per
- * process, so we need to tell the Host which one we're changing (mm->pgd). */
+/*
+ * The Guest calls this after it has set a second-level entry (pte), ie. to map
+ * a page into a process' address space. Wetell the Host the toplevel and
+ * address this corresponds to. The Guest uses one pagetable per process, so
+ * we need to tell the Host which one we're changing (mm->pgd).
+ */
static void lguest_pte_update(struct mm_struct *mm, unsigned long addr,
pte_t *ptep)
{
#ifdef CONFIG_X86_PAE
+ /* PAE needs to hand a 64 bit page table entry, so it uses two args. */
lazy_hcall4(LHCALL_SET_PTE, __pa(mm->pgd), addr,
ptep->pte_low, ptep->pte_high);
#else
@@ -548,6 +652,7 @@ static void lguest_pte_update(struct mm_struct *mm, unsigned long addr,
#endif
}
+/* This is the "set and update" combo-meal-deal version. */
static void lguest_set_pte_at(struct mm_struct *mm, unsigned long addr,
pte_t *ptep, pte_t pteval)
{
@@ -555,10 +660,13 @@ static void lguest_set_pte_at(struct mm_struct *mm, unsigned long addr,
lguest_pte_update(mm, addr, ptep);
}
-/* The Guest calls lguest_set_pud to set a top-level entry and lguest_set_pmd
+/*
+ * The Guest calls lguest_set_pud to set a top-level entry and lguest_set_pmd
* to set a middle-level entry when PAE is activated.
+ *
* Again, we set the entry then tell the Host which page we changed,
- * and the index of the entry we changed. */
+ * and the index of the entry we changed.
+ */
#ifdef CONFIG_X86_PAE
static void lguest_set_pud(pud_t *pudp, pud_t pudval)
{
@@ -577,8 +685,7 @@ static void lguest_set_pmd(pmd_t *pmdp, pmd_t pmdval)
}
#else
-/* The Guest calls lguest_set_pmd to set a top-level entry when PAE is not
- * activated. */
+/* The Guest calls lguest_set_pmd to set a top-level entry when !PAE. */
static void lguest_set_pmd(pmd_t *pmdp, pmd_t pmdval)
{
native_set_pmd(pmdp, pmdval);
@@ -587,7 +694,8 @@ static void lguest_set_pmd(pmd_t *pmdp, pmd_t pmdval)
}
#endif
-/* There are a couple of legacy places where the kernel sets a PTE, but we
+/*
+ * There are a couple of legacy places where the kernel sets a PTE, but we
* don't know the top level any more. This is useless for us, since we don't
* know which pagetable is changing or what address, so we just tell the Host
* to forget all of them. Fortunately, this is very rare.
@@ -595,7 +703,8 @@ static void lguest_set_pmd(pmd_t *pmdp, pmd_t pmdval)
* ... except in early boot when the kernel sets up the initial pagetables,
* which makes booting astonishingly slow: 1.83 seconds! So we don't even tell
* the Host anything changed until we've done the first page table switch,
- * which brings boot back to 0.25 seconds. */
+ * which brings boot back to 0.25 seconds.
+ */
static void lguest_set_pte(pte_t *ptep, pte_t pteval)
{
native_set_pte(ptep, pteval);
@@ -604,6 +713,11 @@ static void lguest_set_pte(pte_t *ptep, pte_t pteval)
}
#ifdef CONFIG_X86_PAE
+/*
+ * With 64-bit PTE values, we need to be careful setting them: if we set 32
+ * bits at a time, the hardware could see a weird half-set entry. These
+ * versions ensure we update all 64 bits at once.
+ */
static void lguest_set_pte_atomic(pte_t *ptep, pte_t pte)
{
native_set_pte_atomic(ptep, pte);
@@ -611,19 +725,21 @@ static void lguest_set_pte_atomic(pte_t *ptep, pte_t pte)
lazy_hcall1(LHCALL_FLUSH_TLB, 1);
}
-void lguest_pte_clear(struct mm_struct *mm, unsigned long addr, pte_t *ptep)
+static void lguest_pte_clear(struct mm_struct *mm, unsigned long addr,
+ pte_t *ptep)
{
native_pte_clear(mm, addr, ptep);
lguest_pte_update(mm, addr, ptep);
}
-void lguest_pmd_clear(pmd_t *pmdp)
+static void lguest_pmd_clear(pmd_t *pmdp)
{
lguest_set_pmd(pmdp, __pmd(0));
}
#endif
-/* Unfortunately for Lguest, the pv_mmu_ops for page tables were based on
+/*
+ * Unfortunately for Lguest, the pv_mmu_ops for page tables were based on
* native page table operations. On native hardware you can set a new page
* table entry whenever you want, but if you want to remove one you have to do
* a TLB flush (a TLB is a little cache of page table entries kept by the CPU).
@@ -632,24 +748,29 @@ void lguest_pmd_clear(pmd_t *pmdp)
* called when a valid entry is written, not when it's removed (ie. marked not
* present). Instead, this is where we come when the Guest wants to remove a
* page table entry: we tell the Host to set that entry to 0 (ie. the present
- * bit is zero). */
+ * bit is zero).
+ */
static void lguest_flush_tlb_single(unsigned long addr)
{
/* Simply set it to zero: if it was not, it will fault back in. */
lazy_hcall3(LHCALL_SET_PTE, lguest_data.pgdir, addr, 0);
}
-/* This is what happens after the Guest has removed a large number of entries.
+/*
+ * This is what happens after the Guest has removed a large number of entries.
* This tells the Host that any of the page table entries for userspace might
- * have changed, ie. virtual addresses below PAGE_OFFSET. */
+ * have changed, ie. virtual addresses below PAGE_OFFSET.
+ */
static void lguest_flush_tlb_user(void)
{
lazy_hcall1(LHCALL_FLUSH_TLB, 0);
}
-/* This is called when the kernel page tables have changed. That's not very
+/*
+ * This is called when the kernel page tables have changed. That's not very
* common (unless the Guest is using highmem, which makes the Guest extremely
- * slow), so it's worth separating this from the user flushing above. */
+ * slow), so it's worth separating this from the user flushing above.
+ */
static void lguest_flush_tlb_kernel(void)
{
lazy_hcall1(LHCALL_FLUSH_TLB, 1);
@@ -686,26 +807,38 @@ static struct irq_chip lguest_irq_controller = {
.unmask = enable_lguest_irq,
};
-/* This sets up the Interrupt Descriptor Table (IDT) entry for each hardware
+/*
+ * This sets up the Interrupt Descriptor Table (IDT) entry for each hardware
* interrupt (except 128, which is used for system calls), and then tells the
* Linux infrastructure that each interrupt is controlled by our level-based
- * lguest interrupt controller. */
+ * lguest interrupt controller.
+ */
static void __init lguest_init_IRQ(void)
{
unsigned int i;
for (i = FIRST_EXTERNAL_VECTOR; i < NR_VECTORS; i++) {
- /* Some systems map "vectors" to interrupts weirdly. Lguest has
- * a straightforward 1 to 1 mapping, so force that here. */
+ /* Some systems map "vectors" to interrupts weirdly. Not us! */
__get_cpu_var(vector_irq)[i] = i - FIRST_EXTERNAL_VECTOR;
if (i != SYSCALL_VECTOR)
set_intr_gate(i, interrupt[i - FIRST_EXTERNAL_VECTOR]);
}
- /* This call is required to set up for 4k stacks, where we have
- * separate stacks for hard and soft interrupts. */
+
+ /*
+ * This call is required to set up for 4k stacks, where we have
+ * separate stacks for hard and soft interrupts.
+ */
irq_ctx_init(smp_processor_id());
}
+/*
+ * With CONFIG_SPARSE_IRQ, interrupt descriptors are allocated as-needed, so
+ * rather than set them in lguest_init_IRQ we are called here every time an
+ * lguest device needs an interrupt.
+ *
+ * FIXME: irq_to_desc_alloc_node() can fail due to lack of memory, we should
+ * pass that up!
+ */
void lguest_setup_irq(unsigned int irq)
{
irq_to_desc_alloc_node(irq, 0);
@@ -724,31 +857,39 @@ static unsigned long lguest_get_wallclock(void)
return lguest_data.time.tv_sec;
}
-/* The TSC is an Intel thing called the Time Stamp Counter. The Host tells us
+/*
+ * The TSC is an Intel thing called the Time Stamp Counter. The Host tells us
* what speed it runs at, or 0 if it's unusable as a reliable clock source.
* This matches what we want here: if we return 0 from this function, the x86
- * TSC clock will give up and not register itself. */
+ * TSC clock will give up and not register itself.
+ */
static unsigned long lguest_tsc_khz(void)
{
return lguest_data.tsc_khz;
}
-/* If we can't use the TSC, the kernel falls back to our lower-priority
- * "lguest_clock", where we read the time value given to us by the Host. */
+/*
+ * If we can't use the TSC, the kernel falls back to our lower-priority
+ * "lguest_clock", where we read the time value given to us by the Host.
+ */
static cycle_t lguest_clock_read(struct clocksource *cs)
{
unsigned long sec, nsec;
- /* Since the time is in two parts (seconds and nanoseconds), we risk
+ /*
+ * Since the time is in two parts (seconds and nanoseconds), we risk
* reading it just as it's changing from 99 & 0.999999999 to 100 and 0,
* and getting 99 and 0. As Linux tends to come apart under the stress
- * of time travel, we must be careful: */
+ * of time travel, we must be careful:
+ */
do {
/* First we read the seconds part. */
sec = lguest_data.time.tv_sec;
- /* This read memory barrier tells the compiler and the CPU that
+ /*
+ * This read memory barrier tells the compiler and the CPU that
* this can't be reordered: we have to complete the above
- * before going on. */
+ * before going on.
+ */
rmb();
/* Now we read the nanoseconds part. */
nsec = lguest_data.time.tv_nsec;
@@ -772,9 +913,11 @@ static struct clocksource lguest_clock = {
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
};
-/* We also need a "struct clock_event_device": Linux asks us to set it to go
+/*
+ * We also need a "struct clock_event_device": Linux asks us to set it to go
* off some time in the future. Actually, James Morris figured all this out, I
- * just applied the patch. */
+ * just applied the patch.
+ */
static int lguest_clockevent_set_next_event(unsigned long delta,
struct clock_event_device *evt)
{
@@ -824,8 +967,10 @@ static struct clock_event_device lguest_clockevent = {
.max_delta_ns = LG_CLOCK_MAX_DELTA,
};
-/* This is the Guest timer interrupt handler (hardware interrupt 0). We just
- * call the clockevent infrastructure and it does whatever needs doing. */
+/*
+ * This is the Guest timer interrupt handler (hardware interrupt 0). We just
+ * call the clockevent infrastructure and it does whatever needs doing.
+ */
static void lguest_time_irq(unsigned int irq, struct irq_desc *desc)
{
unsigned long flags;
@@ -836,10 +981,12 @@ static void lguest_time_irq(unsigned int irq, struct irq_desc *desc)
local_irq_restore(flags);
}
-/* At some point in the boot process, we get asked to set up our timing
+/*
+ * At some point in the boot process, we get asked to set up our timing
* infrastructure. The kernel doesn't expect timer interrupts before this, but
* we cleverly initialized the "blocked_interrupts" field of "struct
- * lguest_data" so that timer interrupts were blocked until now. */
+ * lguest_data" so that timer interrupts were blocked until now.
+ */
static void lguest_time_init(void)
{
/* Set up the timer interrupt (0) to go to our simple timer routine */
@@ -863,14 +1010,16 @@ static void lguest_time_init(void)
* to work. They're pretty simple.
*/
-/* The Guest needs to tell the Host what stack it expects traps to use. For
+/*
+ * The Guest needs to tell the Host what stack it expects traps to use. For
* native hardware, this is part of the Task State Segment mentioned above in
* lguest_load_tr_desc(), but to help hypervisors there's this special call.
*
* We tell the Host the segment we want to use (__KERNEL_DS is the kernel data
* segment), the privilege level (we're privilege level 1, the Host is 0 and
* will not tolerate us trying to use that), the stack pointer, and the number
- * of pages in the stack. */
+ * of pages in the stack.
+ */
static void lguest_load_sp0(struct tss_struct *tss,
struct thread_struct *thread)
{
@@ -884,7 +1033,8 @@ static void lguest_set_debugreg(int regno, unsigned long value)
/* FIXME: Implement */
}
-/* There are times when the kernel wants to make sure that no memory writes are
+/*
+ * There are times when the kernel wants to make sure that no memory writes are
* caught in the cache (that they've all reached real hardware devices). This
* doesn't matter for the Guest which has virtual hardware.
*
@@ -898,11 +1048,13 @@ static void lguest_wbinvd(void)
{
}
-/* If the Guest expects to have an Advanced Programmable Interrupt Controller,
+/*
+ * If the Guest expects to have an Advanced Programmable Interrupt Controller,
* we play dumb by ignoring writes and returning 0 for reads. So it's no
* longer Programmable nor Controlling anything, and I don't think 8 lines of
* code qualifies for Advanced. It will also never interrupt anything. It
- * does, however, allow us to get through the Linux boot code. */
+ * does, however, allow us to get through the Linux boot code.
+ */
#ifdef CONFIG_X86_LOCAL_APIC
static void lguest_apic_write(u32 reg, u32 v)
{
@@ -951,11 +1103,13 @@ static void lguest_safe_halt(void)
kvm_hypercall0(LHCALL_HALT);
}
-/* The SHUTDOWN hypercall takes a string to describe what's happening, and
+/*
+ * The SHUTDOWN hypercall takes a string to describe what's happening, and
* an argument which says whether this to restart (reboot) the Guest or not.
*
* Note that the Host always prefers that the Guest speak in physical addresses
- * rather than virtual addresses, so we use __pa() here. */
+ * rather than virtual addresses, so we use __pa() here.
+ */
static void lguest_power_off(void)
{
kvm_hypercall2(LHCALL_SHUTDOWN, __pa("Power down"),
@@ -986,8 +1140,10 @@ static __init char *lguest_memory_setup(void)
* nice to move it back to lguest_init. Patch welcome... */
atomic_notifier_chain_register(&panic_notifier_list, &paniced);
- /* The Linux bootloader header contains an "e820" memory map: the
- * Launcher populated the first entry with our memory limit. */
+ /*
+ *The Linux bootloader header contains an "e820" memory map: the
+ * Launcher populated the first entry with our memory limit.
+ */
e820_add_region(boot_params.e820_map[0].addr,
boot_params.e820_map[0].size,
boot_params.e820_map[0].type);
@@ -996,16 +1152,17 @@ static __init char *lguest_memory_setup(void)
return "LGUEST";
}
-/* We will eventually use the virtio console device to produce console output,
+/*
+ * We will eventually use the virtio console device to produce console output,
* but before that is set up we use LHCALL_NOTIFY on normal memory to produce
- * console output. */
+ * console output.
+ */
static __init int early_put_chars(u32 vtermno, const char *buf, int count)
{
char scratch[17];
unsigned int len = count;
- /* We use a nul-terminated string, so we have to make a copy. Icky,
- * huh? */
+ /* We use a nul-terminated string, so we make a copy. Icky, huh? */
if (len > sizeof(scratch) - 1)
len = sizeof(scratch) - 1;
scratch[len] = '\0';
@@ -1016,8 +1173,10 @@ static __init int early_put_chars(u32 vtermno, const char *buf, int count)
return len;
}
-/* Rebooting also tells the Host we're finished, but the RESTART flag tells the
- * Launcher to reboot us. */
+/*
+ * Rebooting also tells the Host we're finished, but the RESTART flag tells the
+ * Launcher to reboot us.
+ */
static void lguest_restart(char *reason)
{
kvm_hypercall2(LHCALL_SHUTDOWN, __pa(reason), LGUEST_SHUTDOWN_RESTART);
@@ -1044,7 +1203,8 @@ static void lguest_restart(char *reason)
* fit comfortably.
*
* First we need assembly templates of each of the patchable Guest operations,
- * and these are in i386_head.S. */
+ * and these are in i386_head.S.
+ */
/*G:060 We construct a table from the assembler templates: */
static const struct lguest_insns
@@ -1055,9 +1215,11 @@ static const struct lguest_insns
[PARAVIRT_PATCH(pv_irq_ops.save_fl)] = { lgstart_pushf, lgend_pushf },
};
-/* Now our patch routine is fairly simple (based on the native one in
+/*
+ * Now our patch routine is fairly simple (based on the native one in
* paravirt.c). If we have a replacement, we copy it in and return how much of
- * the available space we used. */
+ * the available space we used.
+ */
static unsigned lguest_patch(u8 type, u16 clobber, void *ibuf,
unsigned long addr, unsigned len)
{
@@ -1069,8 +1231,7 @@ static unsigned lguest_patch(u8 type, u16 clobber, void *ibuf,
insn_len = lguest_insns[type].end - lguest_insns[type].start;
- /* Similarly if we can't fit replacement (shouldn't happen, but let's
- * be thorough). */
+ /* Similarly if it can't fit (doesn't happen, but let's be thorough). */
if (len < insn_len)
return paravirt_patch_default(type, clobber, ibuf, addr, len);
@@ -1079,22 +1240,28 @@ static unsigned lguest_patch(u8 type, u16 clobber, void *ibuf,
return insn_len;
}
-/*G:030 Once we get to lguest_init(), we know we're a Guest. The various
+/*G:029
+ * Once we get to lguest_init(), we know we're a Guest. The various
* pv_ops structures in the kernel provide points for (almost) every routine we
- * have to override to avoid privileged instructions. */
+ * have to override to avoid privileged instructions.
+ */
__init void lguest_init(void)
{
- /* We're under lguest, paravirt is enabled, and we're running at
- * privilege level 1, not 0 as normal. */
+ /* We're under lguest. */
pv_info.name = "lguest";
+ /* Paravirt is enabled. */
pv_info.paravirt_enabled = 1;
+ /* We're running at privilege level 1, not 0 as normal. */
pv_info.kernel_rpl = 1;
+ /* Everyone except Xen runs with this set. */
pv_info.shared_kernel_pmd = 1;
- /* We set up all the lguest overrides for sensitive operations. These
- * are detailed with the operations themselves. */
+ /*
+ * We set up all the lguest overrides for sensitive operations. These
+ * are detailed with the operations themselves.
+ */
- /* interrupt-related operations */
+ /* Interrupt-related operations */
pv_irq_ops.init_IRQ = lguest_init_IRQ;
pv_irq_ops.save_fl = PV_CALLEE_SAVE(save_fl);
pv_irq_ops.restore_fl = __PV_IS_CALLEE_SAVE(lg_restore_fl);
@@ -1102,11 +1269,11 @@ __init void lguest_init(void)
pv_irq_ops.irq_enable = __PV_IS_CALLEE_SAVE(lg_irq_enable);
pv_irq_ops.safe_halt = lguest_safe_halt;
- /* init-time operations */
+ /* Setup operations */
pv_init_ops.memory_setup = lguest_memory_setup;
pv_init_ops.patch = lguest_patch;
- /* Intercepts of various cpu instructions */
+ /* Intercepts of various CPU instructions */
pv_cpu_ops.load_gdt = lguest_load_gdt;
pv_cpu_ops.cpuid = lguest_cpuid;
pv_cpu_ops.load_idt = lguest_load_idt;
@@ -1127,7 +1294,7 @@ __init void lguest_init(void)
pv_cpu_ops.start_context_switch = paravirt_start_context_switch;
pv_cpu_ops.end_context_switch = lguest_end_context_switch;
- /* pagetable management */
+ /* Pagetable management */
pv_mmu_ops.write_cr3 = lguest_write_cr3;
pv_mmu_ops.flush_tlb_user = lguest_flush_tlb_user;
pv_mmu_ops.flush_tlb_single = lguest_flush_tlb_single;
@@ -1149,54 +1316,71 @@ __init void lguest_init(void)
pv_mmu_ops.pte_update_defer = lguest_pte_update;
#ifdef CONFIG_X86_LOCAL_APIC
- /* apic read/write intercepts */
+ /* APIC read/write intercepts */
set_lguest_basic_apic_ops();
#endif
- /* time operations */
+ /* Time operations */
pv_time_ops.get_wallclock = lguest_get_wallclock;
pv_time_ops.time_init = lguest_time_init;
pv_time_ops.get_tsc_khz = lguest_tsc_khz;
- /* Now is a good time to look at the implementations of these functions
- * before returning to the rest of lguest_init(). */
+ /*
+ * Now is a good time to look at the implementations of these functions
+ * before returning to the rest of lguest_init().
+ */
- /*G:070 Now we've seen all the paravirt_ops, we return to
+ /*G:070
+ * Now we've seen all the paravirt_ops, we return to
* lguest_init() where the rest of the fairly chaotic boot setup
- * occurs. */
+ * occurs.
+ */
- /* The stack protector is a weird thing where gcc places a canary
+ /*
+ * The stack protector is a weird thing where gcc places a canary
* value on the stack and then checks it on return. This file is
* compiled with -fno-stack-protector it, so we got this far without
* problems. The value of the canary is kept at offset 20 from the
* %gs register, so we need to set that up before calling C functions
- * in other files. */
+ * in other files.
+ */
setup_stack_canary_segment(0);
- /* We could just call load_stack_canary_segment(), but we might as
- * call switch_to_new_gdt() which loads the whole table and sets up
- * the per-cpu segment descriptor register %fs as well. */
+
+ /*
+ * We could just call load_stack_canary_segment(), but we might as well
+ * call switch_to_new_gdt() which loads the whole table and sets up the
+ * per-cpu segment descriptor register %fs as well.
+ */
switch_to_new_gdt(0);
- /* As described in head_32.S, we map the first 128M of memory. */
+ /* We actually boot with all memory mapped, but let's say 128MB. */
max_pfn_mapped = (128*1024*1024) >> PAGE_SHIFT;
- /* The Host<->Guest Switcher lives at the top of our address space, and
+ /*
+ * The Host<->Guest Switcher lives at the top of our address space, and
* the Host told us how big it is when we made LGUEST_INIT hypercall:
- * it put the answer in lguest_data.reserve_mem */
+ * it put the answer in lguest_data.reserve_mem
+ */
reserve_top_address(lguest_data.reserve_mem);
- /* If we don't initialize the lock dependency checker now, it crashes
- * paravirt_disable_iospace. */
+ /*
+ * If we don't initialize the lock dependency checker now, it crashes
+ * paravirt_disable_iospace.
+ */
lockdep_init();
- /* The IDE code spends about 3 seconds probing for disks: if we reserve
+ /*
+ * The IDE code spends about 3 seconds probing for disks: if we reserve
* all the I/O ports up front it can't get them and so doesn't probe.
* Other device drivers are similar (but less severe). This cuts the
- * kernel boot time on my machine from 4.1 seconds to 0.45 seconds. */
+ * kernel boot time on my machine from 4.1 seconds to 0.45 seconds.
+ */
paravirt_disable_iospace();
- /* This is messy CPU setup stuff which the native boot code does before
- * start_kernel, so we have to do, too: */
+ /*
+ * This is messy CPU setup stuff which the native boot code does before
+ * start_kernel, so we have to do, too:
+ */
cpu_detect(&new_cpu_data);
/* head.S usually sets up the first capability word, so do it here. */
new_cpu_data.x86_capability[0] = cpuid_edx(1);
@@ -1213,22 +1397,28 @@ __init void lguest_init(void)
acpi_ht = 0;
#endif
- /* We set the preferred console to "hvc". This is the "hypervisor
+ /*
+ * We set the preferred console to "hvc". This is the "hypervisor
* virtual console" driver written by the PowerPC people, which we also
- * adapted for lguest's use. */
+ * adapted for lguest's use.
+ */
add_preferred_console("hvc", 0, NULL);
/* Register our very early console. */
virtio_cons_early_init(early_put_chars);
- /* Last of all, we set the power management poweroff hook to point to
+ /*
+ * Last of all, we set the power management poweroff hook to point to
* the Guest routine to power off, and the reboot hook to our restart
- * routine. */
+ * routine.
+ */
pm_power_off = lguest_power_off;
machine_ops.restart = lguest_restart;
- /* Now we're set up, call i386_start_kernel() in head32.c and we proceed
- * to boot as normal. It never returns. */
+ /*
+ * Now we're set up, call i386_start_kernel() in head32.c and we proceed
+ * to boot as normal. It never returns.
+ */
i386_start_kernel();
}
/*