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authorJames Morse <james.morse@arm.com>2016-04-29 18:27:03 +0100
committerAlex Shi <alex.shi@linaro.org>2016-05-31 14:41:29 +0800
commit19daa6ee2da0eaebdf79e44b66a2888f8c74bd7a (patch)
treea3434de75e6f76dcfca7ac8c233ea7771dea59a6
parent9651fc50eeec9690a9bd3cac9a639dabb1b632a9 (diff)
downloadlinux-linaro-stable-19daa6ee2da0eaebdf79e44b66a2888f8c74bd7a.tar.gz
arm64: kvm: Fix kvm teardown for systems using the extended idmap
If memory is located above 1<<VA_BITS, kvm adds an extra level to its page tables, merging the runtime tables and boot tables that contain the idmap. This lets us avoid the trampoline dance during initialisation. This also means there is no trampoline page mapped, so __cpu_reset_hyp_mode() can't call __kvm_hyp_reset() in this page. The good news is the idmap is still mapped, so we don't need the trampoline page. The bad news is we can't call it directly as the idmap is above HYP_PAGE_OFFSET, so its address is masked by kvm_call_hyp. Add a function __extended_idmap_trampoline which will branch into __kvm_hyp_reset in the idmap, change kvm_hyp_reset_entry() to return this address if __kvm_cpu_uses_extended_idmap(). In this case __kvm_hyp_reset() will still switch to the boot tables (which are the merged tables that were already in use), and branch into the idmap (where it already was). This fixes boot failures on these systems, where we fail to execute the missing trampoline page when tearing down kvm in init_subsystems(): [ 2.508922] kvm [1]: 8-bit VMID [ 2.512057] kvm [1]: Hyp mode initialized successfully [ 2.517242] kvm [1]: interrupt-controller@e1140000 IRQ13 [ 2.522622] kvm [1]: timer IRQ3 [ 2.525783] Kernel panic - not syncing: HYP panic: [ 2.525783] PS:200003c9 PC:0000007ffffff820 ESR:86000005 [ 2.525783] FAR:0000007ffffff820 HPFAR:00000000003ffff0 PAR:0000000000000000 [ 2.525783] VCPU: (null) [ 2.525783] [ 2.547667] CPU: 0 PID: 0 Comm: swapper/0 Tainted: G W 4.6.0-rc5+ #1 [ 2.555137] Hardware name: Default string Default string/Default string, BIOS ROD0084E 09/03/2015 [ 2.563994] Call trace: [ 2.566432] [<ffffff80080888d0>] dump_backtrace+0x0/0x240 [ 2.571818] [<ffffff8008088b24>] show_stack+0x14/0x20 [ 2.576858] [<ffffff80083423ac>] dump_stack+0x94/0xb8 [ 2.581899] [<ffffff8008152130>] panic+0x10c/0x250 [ 2.586677] [<ffffff8008152024>] panic+0x0/0x250 [ 2.591281] SMP: stopping secondary CPUs [ 3.649692] SMP: failed to stop secondary CPUs 0-2,4-7 [ 3.654818] Kernel Offset: disabled [ 3.658293] Memory Limit: none [ 3.661337] ---[ end Kernel panic - not syncing: HYP panic: [ 3.661337] PS:200003c9 PC:0000007ffffff820 ESR:86000005 [ 3.661337] FAR:0000007ffffff820 HPFAR:00000000003ffff0 PAR:0000000000000000 [ 3.661337] VCPU: (null) [ 3.661337] Reported-by: Will Deacon <will.deacon@arm.com> Reviewed-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: James Morse <james.morse@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> (cherry picked from commit c612505f860c6d4fac03924879982adcd042e239) Signed-off-by: Alex Shi <alex.shi@linaro.org>
-rw-r--r--arch/arm64/include/asm/kvm_host.h3
-rw-r--r--arch/arm64/kvm/hyp-init.S5
-rw-r--r--arch/arm64/kvm/hyp/entry.S19
-rw-r--r--arch/arm64/kvm/reset.c30
4 files changed, 49 insertions, 8 deletions
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 295fdaafabd5..580a5232d217 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -48,7 +48,8 @@
int __attribute_const__ kvm_target_cpu(void);
int kvm_reset_vcpu(struct kvm_vcpu *vcpu);
int kvm_arch_dev_ioctl_check_extension(long ext);
-phys_addr_t kvm_hyp_reset_entry(void);
+unsigned long kvm_hyp_reset_entry(void);
+void __extended_idmap_trampoline(phys_addr_t boot_pgd, phys_addr_t idmap_start);
struct kvm_arch {
/* The VMID generation used for the virt. memory system */
diff --git a/arch/arm64/kvm/hyp-init.S b/arch/arm64/kvm/hyp-init.S
index 0f474d278987..3270d392970d 100644
--- a/arch/arm64/kvm/hyp-init.S
+++ b/arch/arm64/kvm/hyp-init.S
@@ -142,6 +142,11 @@ merged:
ENDPROC(__kvm_hyp_init)
/*
+ * Reset kvm back to the hyp stub. This is the trampoline dance in
+ * reverse. If kvm used an extended idmap, __extended_idmap_trampoline
+ * calls this code directly in the idmap. In this case switching to the
+ * boot tables is a no-op.
+ *
* x0: HYP boot pgd
* x1: HYP phys_idmap_start
*/
diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
index 1050b2b09904..ac65c52d6275 100644
--- a/arch/arm64/kvm/hyp/entry.S
+++ b/arch/arm64/kvm/hyp/entry.S
@@ -159,3 +159,22 @@ ENTRY(__fpsimd_guest_restore)
eret
ENDPROC(__fpsimd_guest_restore)
+
+/*
+ * When using the extended idmap, we don't have a trampoline page we can use
+ * while we switch pages tables during __kvm_hyp_reset. Accessing the idmap
+ * directly would be ideal, but if we're using the extended idmap then the
+ * idmap is located above HYP_PAGE_OFFSET, and the address will be masked by
+ * kvm_call_hyp using kern_hyp_va.
+ *
+ * x0: HYP boot pgd
+ * x1: HYP phys_idmap_start
+ */
+ENTRY(__extended_idmap_trampoline)
+ mov x4, x1
+ adr_l x3, __kvm_hyp_reset
+
+ /* insert __kvm_hyp_reset()s offset into phys_idmap_start */
+ bfi x4, x3, #0, #PAGE_SHIFT
+ br x4
+ENDPROC(__extended_idmap_trampoline)
diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
index 03e909069691..e515b85220b4 100644
--- a/arch/arm64/kvm/reset.c
+++ b/arch/arm64/kvm/reset.c
@@ -114,12 +114,28 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
extern char __hyp_idmap_text_start[];
-phys_addr_t kvm_hyp_reset_entry(void)
+unsigned long kvm_hyp_reset_entry(void)
{
- unsigned long offset;
-
- offset = (unsigned long)__kvm_hyp_reset
- - ((unsigned long)__hyp_idmap_text_start & PAGE_MASK);
-
- return TRAMPOLINE_VA + offset;
+ if (!__kvm_cpu_uses_extended_idmap()) {
+ unsigned long offset;
+
+ /*
+ * Find the address of __kvm_hyp_reset() in the trampoline page.
+ * This is present in the running page tables, and the boot page
+ * tables, so we call the code here to start the trampoline
+ * dance in reverse.
+ */
+ offset = (unsigned long)__kvm_hyp_reset
+ - ((unsigned long)__hyp_idmap_text_start & PAGE_MASK);
+
+ return TRAMPOLINE_VA + offset;
+ } else {
+ /*
+ * KVM is running with merged page tables, which don't have the
+ * trampoline page mapped. We know the idmap is still mapped,
+ * but can't be called into directly. Use
+ * __extended_idmap_trampoline to do the call.
+ */
+ return (unsigned long)kvm_ksym_ref(__extended_idmap_trampoline);
+ }
}