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kvm: x86: Skip TLB flush on fast CR3 switch when indicated by guest

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When PCIDs are enabled, the MSb of the source operand for a MOV-to-CR3
instruction indicates that the TLB doesn't need to be flushed.

This change enables this optimization for MOV-to-CR3s in the guest
that have been intercepted by KVM for shadow paging and are handled
within the fast CR3 switch path.

Signed-off-by: Junaid Shahid <junaids@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Junaid Shahid
2018-06-27 14:59:15 -07:00
committed by Paolo Bonzini
parent eb4b248e15
commit ade61e2824
4 changed files with 36 additions and 17 deletions
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28
arch/x86/kvm/mmu.c
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@@ -4037,7 +4037,8 @@ static void nonpaging_init_context(struct kvm_vcpu *vcpu,
}
static bool fast_cr3_switch(struct kvm_vcpu *vcpu, gpa_t new_cr3,
union kvm_mmu_page_role new_role)
union kvm_mmu_page_role new_role,
bool skip_tlb_flush)
{
struct kvm_mmu *mmu = &vcpu->arch.mmu;
@@ -4070,7 +4071,9 @@ static bool fast_cr3_switch(struct kvm_vcpu *vcpu, gpa_t new_cr3,
kvm_make_request(KVM_REQ_LOAD_CR3, vcpu);
kvm_make_request(KVM_REQ_MMU_SYNC, vcpu);
kvm_x86_ops->tlb_flush(vcpu, true);
if (!skip_tlb_flush)
kvm_x86_ops->tlb_flush(vcpu, true);
__clear_sp_write_flooding_count(
page_header(mmu->root_hpa));
@@ -4082,15 +4085,17 @@ static bool fast_cr3_switch(struct kvm_vcpu *vcpu, gpa_t new_cr3,
}
static void __kvm_mmu_new_cr3(struct kvm_vcpu *vcpu, gpa_t new_cr3,
union kvm_mmu_page_role new_role)
union kvm_mmu_page_role new_role,
bool skip_tlb_flush)
{
if (!fast_cr3_switch(vcpu, new_cr3, new_role))
if (!fast_cr3_switch(vcpu, new_cr3, new_role, skip_tlb_flush))
kvm_mmu_free_roots(vcpu, false);
}
void kvm_mmu_new_cr3(struct kvm_vcpu *vcpu, gpa_t new_cr3)
void kvm_mmu_new_cr3(struct kvm_vcpu *vcpu, gpa_t new_cr3, bool skip_tlb_flush)
{
__kvm_mmu_new_cr3(vcpu, new_cr3, kvm_mmu_calc_root_page_role(vcpu));
__kvm_mmu_new_cr3(vcpu, new_cr3, kvm_mmu_calc_root_page_role(vcpu),
skip_tlb_flush);
}
EXPORT_SYMBOL_GPL(kvm_mmu_new_cr3);
@@ -4733,7 +4738,7 @@ void kvm_init_shadow_ept_mmu(struct kvm_vcpu *vcpu, bool execonly,
union kvm_mmu_page_role root_page_role =
kvm_calc_shadow_ept_root_page_role(vcpu, accessed_dirty);
__kvm_mmu_new_cr3(vcpu, new_eptp, root_page_role);
__kvm_mmu_new_cr3(vcpu, new_eptp, root_page_role, false);
context->shadow_root_level = PT64_ROOT_4LEVEL;
context->nx = true;
@@ -5196,11 +5201,16 @@ void kvm_mmu_invpcid_gva(struct kvm_vcpu *vcpu, gva_t gva, unsigned long pcid)
kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
}
if (VALID_PAGE(mmu->prev_root.hpa) &&
pcid == kvm_get_pcid(vcpu, mmu->prev_root.cr3))
kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
++vcpu->stat.invlpg;
/*
* Mappings not reachable via the current cr3 will be synced when
* switching to that cr3, so nothing needs to be done here for them.
* Mappings not reachable via the current cr3 or the prev_root.cr3 will
* be synced when switching to that cr3, so nothing needs to be done
* here for them.
*/
}
EXPORT_SYMBOL_GPL(kvm_mmu_invpcid_gva);