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KVM: MMU: Fix rare oops on guest context switch 

A guest context switch to an uncached cr3 can require allocation of
shadow pages, but we only recycle shadow pages in kvm_mmu_page_fault().

Move shadow page recycling to mmu_topup_memory_caches(), which is called
from both the page fault handler and from guest cr3 reload.

Signed-off-by: Avi Kivity <avi@qumranet.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Avi Kivity 2007-09-14 20:26:06 +03:00 committed by Linus Torvalds
parent 44e3ff32ac
commit 22d95b1282
2 changed files with 10 additions and 5 deletions
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10
drivers/kvm/kvm.h
View File

@ -619,7 +619,7 @@ unsigned long segment_base(u16 selector);
void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
const u8 *old, const u8 *new, int bytes);
int kvm_mmu_unprotect_page_virt(struct kvm_vcpu *vcpu, gva_t gva);
void kvm_mmu_free_some_pages(struct kvm_vcpu *vcpu);
void __kvm_mmu_free_some_pages(struct kvm_vcpu *vcpu);
int kvm_mmu_load(struct kvm_vcpu *vcpu);
void kvm_mmu_unload(struct kvm_vcpu *vcpu);
@ -628,11 +628,15 @@ int kvm_hypercall(struct kvm_vcpu *vcpu, struct kvm_run *run);
static inline int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t gva,
u32 error_code)
{
if (unlikely(vcpu->kvm->n_free_mmu_pages < KVM_MIN_FREE_MMU_PAGES))
kvm_mmu_free_some_pages(vcpu);
return vcpu->mmu.page_fault(vcpu, gva, error_code);
}
static inline void kvm_mmu_free_some_pages(struct kvm_vcpu *vcpu)
{
if (unlikely(vcpu->kvm->n_free_mmu_pages < KVM_MIN_FREE_MMU_PAGES))
__kvm_mmu_free_some_pages(vcpu);
}
static inline int kvm_mmu_reload(struct kvm_vcpu *vcpu)
{
if (likely(vcpu->mmu.root_hpa != INVALID_PAGE))

5
drivers/kvm/mmu.c
View File

@ -273,12 +273,14 @@ static int mmu_topup_memory_caches(struct kvm_vcpu *vcpu)
int r;
r = __mmu_topup_memory_caches(vcpu, GFP_NOWAIT);
kvm_mmu_free_some_pages(vcpu);
if (r < 0) {
spin_unlock(&vcpu->kvm->lock);
kvm_arch_ops->vcpu_put(vcpu);
r = __mmu_topup_memory_caches(vcpu, GFP_KERNEL);
kvm_arch_ops->vcpu_load(vcpu);
spin_lock(&vcpu->kvm->lock);
kvm_mmu_free_some_pages(vcpu);
}
return r;
}
@ -1208,7 +1210,7 @@ int kvm_mmu_unprotect_page_virt(struct kvm_vcpu *vcpu, gva_t gva)
return kvm_mmu_unprotect_page(vcpu, gpa >> PAGE_SHIFT);
}
void kvm_mmu_free_some_pages(struct kvm_vcpu *vcpu)
void __kvm_mmu_free_some_pages(struct kvm_vcpu *vcpu)
{
while (vcpu->kvm->n_free_mmu_pages < KVM_REFILL_PAGES) {
struct kvm_mmu_page *page;
@ -1218,7 +1220,6 @@ void kvm_mmu_free_some_pages(struct kvm_vcpu *vcpu)
kvm_mmu_zap_page(vcpu->kvm, page);
}
}
EXPORT_SYMBOL_GPL(kvm_mmu_free_some_pages);
static void free_mmu_pages(struct kvm_vcpu *vcpu)
{