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KVM: X86: Don't unload MMU in kvm_vcpu_flush_tlb_guest()

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kvm_mmu_unload() destroys all the PGD caches.  Use the lighter
kvm_mmu_sync_roots() and kvm_mmu_sync_prev_roots() instead.

Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Message-Id: <20211019110154.4091-5-jiangshanlai@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Lai Jiangshan 2021-10-19 19:01:54 +08:00 committed by Paolo Bonzini
parent 264d3dc1d3
commit 61b05a9fd4
3 changed files with 22 additions and 6 deletions
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1
arch/x86/kvm/mmu.h
View File

@ -79,6 +79,7 @@ int kvm_handle_page_fault(struct kvm_vcpu *vcpu, u64 error_code,
int kvm_mmu_load(struct kvm_vcpu *vcpu);
void kvm_mmu_unload(struct kvm_vcpu *vcpu);
void kvm_mmu_sync_roots(struct kvm_vcpu *vcpu);
void kvm_mmu_sync_prev_roots(struct kvm_vcpu *vcpu);
static inline int kvm_mmu_reload(struct kvm_vcpu *vcpu)
{

16
arch/x86/kvm/mmu/mmu.c
View File

@ -3647,6 +3647,9 @@ static bool is_unsync_root(hpa_t root)
{
struct kvm_mmu_page *sp;
if (!VALID_PAGE(root))
return false;
/*
* The read barrier orders the CPU's read of SPTE.W during the page table
* walk before the reads of sp->unsync/sp->unsync_children here.
@ -3714,6 +3717,19 @@ void kvm_mmu_sync_roots(struct kvm_vcpu *vcpu)
write_unlock(&vcpu->kvm->mmu_lock);
}
void kvm_mmu_sync_prev_roots(struct kvm_vcpu *vcpu)
{
unsigned long roots_to_free = 0;
int i;
for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++)
if (is_unsync_root(vcpu->arch.mmu->prev_roots[i].hpa))
roots_to_free |= KVM_MMU_ROOT_PREVIOUS(i);
/* sync prev_roots by simply freeing them */
kvm_mmu_free_roots(vcpu, vcpu->arch.mmu, roots_to_free);
}
static gpa_t nonpaging_gva_to_gpa(struct kvm_vcpu *vcpu, gpa_t vaddr,
u32 access, struct x86_exception *exception)
{

11
arch/x86/kvm/x86.c
View File

@ -3245,15 +3245,14 @@ static void kvm_vcpu_flush_tlb_guest(struct kvm_vcpu *vcpu)
++vcpu->stat.tlb_flush;
if (!tdp_enabled) {
/*
/*
* A TLB flush on behalf of the guest is equivalent to
* INVPCID(all), toggling CR4.PGE, etc., which requires
* a forced sync of the shadow page tables. Unload the
* entire MMU here and the subsequent load will sync the
* shadow page tables, and also flush the TLB.
* a forced sync of the shadow page tables. Ensure all the
* roots are synced and the guest TLB in hardware is clean.
*/
kvm_mmu_unload(vcpu);
return;
kvm_mmu_sync_roots(vcpu);
kvm_mmu_sync_prev_roots(vcpu);
}
static_call(kvm_x86_tlb_flush_guest)(vcpu);