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-rw-r--r--arch/x86/xen/mmu.c318
1 files changed, 242 insertions, 76 deletions
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 00969099b05..d4c7265cf0a 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -170,51 +170,162 @@ DEFINE_PER_CPU(unsigned long, xen_current_cr3); /* actual vcpu cr3 */
*/
#define USER_LIMIT ((STACK_TOP_MAX + PGDIR_SIZE - 1) & PGDIR_MASK)
-static unsigned long max_p2m_pfn __read_mostly = MAX_DOMAIN_PAGES;
+/*
+ * Xen leaves the responsibility for maintaining p2m mappings to the
+ * guests themselves, but it must also access and update the p2m array
+ * during suspend/resume when all the pages are reallocated.
+ *
+ * The p2m table is logically a flat array, but we implement it as a
+ * three-level tree to allow the address space to be sparse.
+ *
+ * Xen
+ * |
+ * p2m_top p2m_top_mfn
+ * / \ / \
+ * p2m_mid p2m_mid p2m_mid_mfn p2m_mid_mfn
+ * / \ / \ / /
+ * p2m p2m p2m p2m p2m p2m p2m ...
+ *
+ * The p2m_top and p2m_top_mfn levels are limited to 1 page, so the
+ * maximum representable pseudo-physical address space is:
+ * P2M_TOP_PER_PAGE * P2M_MID_PER_PAGE * P2M_PER_PAGE pages
+ *
+ * P2M_PER_PAGE depends on the architecture, as a mfn is always
+ * unsigned long (8 bytes on 64-bit, 4 bytes on 32), leading to
+ * 512 and 1024 entries respectively.
+ */
-#define P2M_ENTRIES_PER_PAGE (PAGE_SIZE / sizeof(unsigned long))
-#define TOP_ENTRIES(pages) ((pages) / P2M_ENTRIES_PER_PAGE)
-#define MAX_TOP_ENTRIES TOP_ENTRIES(MAX_DOMAIN_PAGES)
+static unsigned long max_p2m_pfn __read_mostly;
-/* Placeholder for holes in the address space */
-static RESERVE_BRK_ARRAY(unsigned long, p2m_missing, P2M_ENTRIES_PER_PAGE);
+#define P2M_PER_PAGE (PAGE_SIZE / sizeof(unsigned long))
+#define P2M_MID_PER_PAGE (PAGE_SIZE / sizeof(unsigned long *))
+#define P2M_TOP_PER_PAGE (PAGE_SIZE / sizeof(unsigned long **))
- /* Array of pointers to pages containing p2m entries */
-static RESERVE_BRK_ARRAY(unsigned long *, p2m_top, MAX_TOP_ENTRIES);
+#define MAX_P2M_PFN (P2M_TOP_PER_PAGE * P2M_MID_PER_PAGE * P2M_PER_PAGE)
-/* Arrays of p2m arrays expressed in mfns used for save/restore */
-static RESERVE_BRK_ARRAY(unsigned long, p2m_top_mfn, MAX_TOP_ENTRIES);
+/* Placeholders for holes in the address space */
+static RESERVE_BRK_ARRAY(unsigned long, p2m_missing, P2M_PER_PAGE);
+static RESERVE_BRK_ARRAY(unsigned long *, p2m_mid_missing, P2M_MID_PER_PAGE);
+static RESERVE_BRK_ARRAY(unsigned long, p2m_mid_missing_mfn, P2M_MID_PER_PAGE);
-static RESERVE_BRK_ARRAY(unsigned long, p2m_top_mfn_list,
- (MAX_TOP_ENTRIES / P2M_ENTRIES_PER_PAGE));
+static RESERVE_BRK_ARRAY(unsigned long **, p2m_top, P2M_TOP_PER_PAGE);
+static RESERVE_BRK_ARRAY(unsigned long, p2m_top_mfn, P2M_TOP_PER_PAGE);
+
+RESERVE_BRK(p2m_mid, PAGE_SIZE * (MAX_DOMAIN_PAGES / (P2M_PER_PAGE * P2M_MID_PER_PAGE)));
+RESERVE_BRK(p2m_mid_mfn, PAGE_SIZE * (MAX_DOMAIN_PAGES / (P2M_PER_PAGE * P2M_MID_PER_PAGE)));
static inline unsigned p2m_top_index(unsigned long pfn)
{
- BUG_ON(pfn >= max_p2m_pfn);
- return pfn / P2M_ENTRIES_PER_PAGE;
+ BUG_ON(pfn >= MAX_P2M_PFN);
+ return pfn / (P2M_MID_PER_PAGE * P2M_PER_PAGE);
+}
+
+static inline unsigned p2m_mid_index(unsigned long pfn)
+{
+ return (pfn / P2M_PER_PAGE) % P2M_MID_PER_PAGE;
}
static inline unsigned p2m_index(unsigned long pfn)
{
- return pfn % P2M_ENTRIES_PER_PAGE;
+ return pfn % P2M_PER_PAGE;
}
-/* Build the parallel p2m_top_mfn structures */
+static void p2m_top_init(unsigned long ***top)
+{
+ unsigned i;
+
+ for (i = 0; i < P2M_TOP_PER_PAGE; i++)
+ top[i] = p2m_mid_missing;
+}
+
+static void p2m_top_mfn_init(unsigned long *top)
+{
+ unsigned i;
+
+ for (i = 0; i < P2M_TOP_PER_PAGE; i++)
+ top[i] = virt_to_mfn(p2m_mid_missing_mfn);
+}
+
+static void p2m_mid_init(unsigned long **mid)
+{
+ unsigned i;
+
+ for (i = 0; i < P2M_MID_PER_PAGE; i++)
+ mid[i] = p2m_missing;
+}
+
+static void p2m_mid_mfn_init(unsigned long *mid)
+{
+ unsigned i;
+
+ for (i = 0; i < P2M_MID_PER_PAGE; i++)
+ mid[i] = virt_to_mfn(p2m_missing);
+}
+
+static void p2m_init(unsigned long *p2m)
+{
+ unsigned i;
+
+ for (i = 0; i < P2M_MID_PER_PAGE; i++)
+ p2m[i] = INVALID_P2M_ENTRY;
+}
+
+/*
+ * Build the parallel p2m_top_mfn and p2m_mid_mfn structures
+ *
+ * This is called both at boot time, and after resuming from suspend:
+ * - At boot time we're called very early, and must use extend_brk()
+ * to allocate memory.
+ *
+ * - After resume we're called from within stop_machine, but the mfn
+ * tree should alreay be completely allocated.
+ */
void xen_build_mfn_list_list(void)
{
- unsigned pfn, idx;
+ unsigned pfn, i;
- for (pfn = 0; pfn < max_p2m_pfn; pfn += P2M_ENTRIES_PER_PAGE) {
- unsigned topidx = p2m_top_index(pfn);
+ /* Pre-initialize p2m_top_mfn to be completely missing */
+ if (p2m_top_mfn == NULL) {
+ p2m_mid_missing_mfn = extend_brk(PAGE_SIZE, PAGE_SIZE);
+ p2m_mid_mfn_init(p2m_mid_missing_mfn);
- p2m_top_mfn[topidx] = virt_to_mfn(p2m_top[topidx]);
+ p2m_top_mfn = extend_brk(PAGE_SIZE, PAGE_SIZE);
+ p2m_top_mfn_init(p2m_top_mfn);
}
- for (idx = 0;
- idx < TOP_ENTRIES(max_p2m_pfn)/P2M_ENTRIES_PER_PAGE;
- idx++) {
- unsigned topidx = idx * P2M_ENTRIES_PER_PAGE;
- p2m_top_mfn_list[idx] = virt_to_mfn(&p2m_top_mfn[topidx]);
+ for (pfn = 0; pfn < max_p2m_pfn; pfn += P2M_PER_PAGE) {
+ unsigned topidx = p2m_top_index(pfn);
+ unsigned mididx = p2m_mid_index(pfn);
+ unsigned long **mid;
+ unsigned long mid_mfn;
+ unsigned long *mid_mfn_p;
+
+ mid = p2m_top[topidx];
+
+ /* Don't bother allocating any mfn mid levels if
+ they're just missing */
+ if (mid[mididx] == p2m_missing)
+ continue;
+
+ mid_mfn = p2m_top_mfn[topidx];
+ mid_mfn_p = mfn_to_virt(mid_mfn);
+
+ if (mid_mfn_p == p2m_mid_missing_mfn) {
+ /*
+ * XXX boot-time only! We should never find
+ * missing parts of the mfn tree after
+ * runtime. extend_brk() will BUG if we call
+ * it too late.
+ */
+ mid_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE);
+ p2m_mid_mfn_init(mid_mfn_p);
+
+ mid_mfn = virt_to_mfn(mid_mfn_p);
+
+ p2m_top_mfn[topidx] = mid_mfn;
+ }
+
+ mid_mfn_p[mididx] = virt_to_mfn(mid[mididx]);
}
}
@@ -223,7 +334,7 @@ void xen_setup_mfn_list_list(void)
BUG_ON(HYPERVISOR_shared_info == &xen_dummy_shared_info);
HYPERVISOR_shared_info->arch.pfn_to_mfn_frame_list_list =
- virt_to_mfn(p2m_top_mfn_list);
+ virt_to_mfn(p2m_top_mfn);
HYPERVISOR_shared_info->arch.max_pfn = max_p2m_pfn;
}
@@ -233,99 +344,154 @@ void __init xen_build_dynamic_phys_to_machine(void)
unsigned long *mfn_list = (unsigned long *)xen_start_info->mfn_list;
unsigned long max_pfn = min(MAX_DOMAIN_PAGES, xen_start_info->nr_pages);
unsigned pfn;
- unsigned i;
max_p2m_pfn = max_pfn;
- p2m_missing = extend_brk(sizeof(*p2m_missing) * P2M_ENTRIES_PER_PAGE,
- PAGE_SIZE);
- for (i = 0; i < P2M_ENTRIES_PER_PAGE; i++)
- p2m_missing[i] = ~0UL;
+ p2m_missing = extend_brk(PAGE_SIZE, PAGE_SIZE);
+ p2m_init(p2m_missing);
- p2m_top = extend_brk(sizeof(*p2m_top) * TOP_ENTRIES(max_pfn),
- PAGE_SIZE);
- for (i = 0; i < TOP_ENTRIES(max_pfn); i++)
- p2m_top[i] = p2m_missing;
+ p2m_mid_missing = extend_brk(PAGE_SIZE, PAGE_SIZE);
+ p2m_mid_init(p2m_mid_missing);
- p2m_top_mfn = extend_brk(sizeof(*p2m_top_mfn) * TOP_ENTRIES(max_pfn),
- PAGE_SIZE);
- p2m_top_mfn_list = extend_brk(sizeof(*p2m_top_mfn_list) *
- (TOP_ENTRIES(max_pfn) / P2M_ENTRIES_PER_PAGE),
- PAGE_SIZE);
+ p2m_top = extend_brk(PAGE_SIZE, PAGE_SIZE);
+ p2m_top_init(p2m_top);
- for (pfn = 0; pfn < max_pfn; pfn += P2M_ENTRIES_PER_PAGE) {
+ /*
+ * The domain builder gives us a pre-constructed p2m array in
+ * mfn_list for all the pages initially given to us, so we just
+ * need to graft that into our tree structure.
+ */
+ for (pfn = 0; pfn < max_pfn; pfn += P2M_PER_PAGE) {
unsigned topidx = p2m_top_index(pfn);
+ unsigned mididx = p2m_mid_index(pfn);
+
+ if (p2m_top[topidx] == p2m_mid_missing) {
+ unsigned long **mid = extend_brk(PAGE_SIZE, PAGE_SIZE);
+ p2m_mid_init(mid);
- p2m_top[topidx] = &mfn_list[pfn];
+ p2m_top[topidx] = mid;
+ }
+
+ p2m_top[topidx][mididx] = &mfn_list[pfn];
}
+ /* Allocate and initialize top and mid mfn levels */
xen_build_mfn_list_list();
}
unsigned long get_phys_to_machine(unsigned long pfn)
{
- unsigned topidx, idx;
+ unsigned topidx, mididx, idx;
- if (unlikely(pfn >= max_p2m_pfn))
+ if (unlikely(pfn >= MAX_P2M_PFN))
return INVALID_P2M_ENTRY;
topidx = p2m_top_index(pfn);
+ mididx = p2m_mid_index(pfn);
idx = p2m_index(pfn);
- return p2m_top[topidx][idx];
+
+ return p2m_top[topidx][mididx][idx];
}
EXPORT_SYMBOL_GPL(get_phys_to_machine);
-/* install a new p2m_top page */
-static bool install_p2mtop_page(unsigned long pfn, unsigned long *p)
+static void *alloc_p2m_page(void)
{
- unsigned topidx = p2m_top_index(pfn);
- unsigned long **pfnp, *mfnp;
- unsigned i;
+ return (void *)__get_free_page(GFP_KERNEL | __GFP_REPEAT);
+}
- pfnp = &p2m_top[topidx];
- mfnp = &p2m_top_mfn[topidx];
+static void free_p2m_page(void *p)
+{
+ free_page((unsigned long)p);
+}
- for (i = 0; i < P2M_ENTRIES_PER_PAGE; i++)
- p[i] = INVALID_P2M_ENTRY;
+/*
+ * Fully allocate the p2m structure for a given pfn. We need to check
+ * that both the top and mid levels are allocated, and make sure the
+ * parallel mfn tree is kept in sync. We may race with other cpus, so
+ * the new pages are installed with cmpxchg; if we lose the race then
+ * simply free the page we allocated and use the one that's there.
+ */
+static bool alloc_p2m(unsigned long pfn)
+{
+ unsigned topidx, mididx;
+ unsigned long ***top_p, **mid;
+ unsigned long *top_mfn_p, *mid_mfn;
- if (cmpxchg(pfnp, p2m_missing, p) == p2m_missing) {
- *mfnp = virt_to_mfn(p);
- return true;
+ topidx = p2m_top_index(pfn);
+ mididx = p2m_mid_index(pfn);
+
+ top_p = &p2m_top[topidx];
+ mid = *top_p;
+
+ if (mid == p2m_mid_missing) {
+ /* Mid level is missing, allocate a new one */
+ mid = alloc_p2m_page();
+ if (!mid)
+ return false;
+
+ p2m_mid_init(mid);
+
+ if (cmpxchg(top_p, p2m_mid_missing, mid) != p2m_mid_missing)
+ free_p2m_page(mid);
}
- return false;
-}
+ top_mfn_p = &p2m_top_mfn[topidx];
+ mid_mfn = mfn_to_virt(*top_mfn_p);
-static void alloc_p2m(unsigned long pfn)
-{
- unsigned long *p;
+ if (mid_mfn == p2m_mid_missing_mfn) {
+ /* Separately check the mid mfn level */
+ unsigned long missing_mfn;
+ unsigned long mid_mfn_mfn;
+
+ mid_mfn = alloc_p2m_page();
+ if (!mid_mfn)
+ return false;
+
+ p2m_mid_mfn_init(mid_mfn);
+
+ missing_mfn = virt_to_mfn(p2m_mid_missing_mfn);
+ mid_mfn_mfn = virt_to_mfn(mid_mfn);
+ if (cmpxchg(top_mfn_p, missing_mfn, mid_mfn_mfn) != missing_mfn)
+ free_p2m_page(mid_mfn);
+ }
- p = (void *)__get_free_page(GFP_KERNEL | __GFP_NOFAIL);
- BUG_ON(p == NULL);
+ if (p2m_top[topidx][mididx] == p2m_missing) {
+ /* p2m leaf page is missing */
+ unsigned long *p2m;
- if (!install_p2mtop_page(pfn, p))
- free_page((unsigned long)p);
+ p2m = alloc_p2m_page();
+ if (!p2m)
+ return false;
+
+ p2m_init(p2m);
+
+ if (cmpxchg(&mid[mididx], p2m_missing, p2m) != p2m_missing)
+ free_p2m_page(p2m);
+ else
+ mid_mfn[mididx] = virt_to_mfn(p2m);
+ }
+
+ return true;
}
/* Try to install p2m mapping; fail if intermediate bits missing */
bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
{
- unsigned topidx, idx;
+ unsigned topidx, mididx, idx;
- if (unlikely(pfn >= max_p2m_pfn)) {
+ if (unlikely(pfn >= MAX_P2M_PFN)) {
BUG_ON(mfn != INVALID_P2M_ENTRY);
return true;
}
topidx = p2m_top_index(pfn);
- if (p2m_top[topidx] == p2m_missing) {
- if (mfn == INVALID_P2M_ENTRY)
- return true;
- return false;
- }
-
+ mididx = p2m_mid_index(pfn);
idx = p2m_index(pfn);
- p2m_top[topidx][idx] = mfn;
+
+ if (p2m_top[topidx][mididx] == p2m_missing)
+ return mfn == INVALID_P2M_ENTRY;
+
+ p2m_top[topidx][mididx][idx] = mfn;
return true;
}
@@ -338,7 +504,7 @@ void set_phys_to_machine(unsigned long pfn, unsigned long mfn)
}
if (unlikely(!__set_phys_to_machine(pfn, mfn))) {
- alloc_p2m(pfn);
+ WARN(!alloc_p2m(pfn), "Can't allocate p2m for %lx, %lx", pfn, mfn);
if (!__set_phys_to_machine(pfn, mfn))
BUG();