On Tue, Jun 12, 2018 at 03:52:42PM -0700, Junaid Shahid wrote:
> When the guest indicates that the TLB doesn't need to be flushed in a
> CR3 switch, we can also skip resyncing the shadow page tables since an
> out-of-sync shadow page table is equivalent to an out-of-sync TLB.
>
> Signed-off-by: Junaid Shahid <junaids@xxxxxxxxxx>
> ---
> arch/x86/kvm/mmu.c | 38 +++++++++++++++++++++++++++++++++-----
> arch/x86/kvm/vmx.c | 11 ++++++-----
> arch/x86/kvm/x86.c | 6 +++---
> 3 files changed, 42 insertions(+), 13 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 4464565eec96..5b26c191052c 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -4087,9 +4087,19 @@ 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);
> - if (!skip_tlb_flush)
> + if (!skip_tlb_flush) {
> + kvm_make_request(KVM_REQ_MMU_SYNC, vcpu);
> kvm_x86_ops->tlb_flush(vcpu, true);
> + }
> +
> + /*
> + * The last MMIO access's GVA and GPA are cached in the
> + * VCPU. When switching to a new CR3, that GVA->GPA
> + * mapping may no longer be valid. So clear any cached
> + * MMIO info even when we don't need to sync the shadow
> + * page tables.
> + */
> + vcpu_clear_mmio_info(vcpu, MMIO_GVA_ANY);
>
> __clear_sp_write_flooding_count(
> page_header(mmu->root_hpa));
> @@ -5205,6 +5215,21 @@ void kvm_mmu_invlpg(struct kvm_vcpu *vcpu, gva_t gva)
> struct kvm_mmu *mmu = &vcpu->arch.mmu;
>
> mmu->invlpg(vcpu, gva, mmu->root_hpa);
> +
> + /*
> + * INVLPG is required to invalidate any global mappings for the VA,
> + * irrespective of PCID. Since it would take us roughly similar amount
> + * of work to determine whether the prev_root mapping of the VA is
> + * marked global, or to just sync it blindly, so we might as well just
> + * always sync it.
> + *
> + * 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.
> + */
> + if (VALID_PAGE(mmu->prev_root.hpa))
> + mmu->invlpg(vcpu, gva, mmu->prev_root.hpa);
> +
> kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
> ++vcpu->stat.invlpg;
> }
> @@ -5220,14 +5245,17 @@ void kvm_mmu_invpcid_gva(struct kvm_vcpu *vcpu, gva_t gva, unsigned long pcid)
> }
>
> if (VALID_PAGE(mmu->prev_root.hpa) &&
> - pcid == kvm_get_pcid(vcpu, mmu->prev_root.cr3))
> + pcid == kvm_get_pcid(vcpu, mmu->prev_root.cr3)) {
> + mmu->invlpg(vcpu, gva, mmu->prev_root.hpa);
> 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 synced 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);
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index ac4e78c2da38..98b2a9ca3ba9 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -8682,14 +8682,15 @@ static int handle_invpcid(struct kvm_vcpu *vcpu)
> kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
> }
>
> - if (kvm_get_pcid(vcpu, vcpu->arch.mmu.prev_root.cr3)
> + if (kvm_get_pcid(vcpu, vcpu->arch.mmu.prev_root.cr3)
Trailing whitespace is being addded.
> == operand.pcid)
> - kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
> + kvm_mmu_free_roots(vcpu, KVM_MMU_ROOT_PREVIOUS);
> +
Extra newline isn't needed.
>
> /*
> - * If the current cr3 does not use the given PCID, then nothing
> - * needs to be synced here because a resync will happen anyway
> - * before switching to any other CR3.
> + * If neither the current cr3 nor the prev_root.cr3 use the
> + * given PCID, then nothing needs to be done here because a
> + * resync will happen anyway before switching to any other CR3.
> */
>
> skip_emulated_instruction(vcpu);
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 151a8f61c7f1..6a179f54b42c 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -858,10 +858,10 @@ int kvm_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3)
> #endif
>
> if (cr3 == kvm_read_cr3(vcpu) && !pdptrs_changed(vcpu)) {
> - kvm_mmu_sync_roots(vcpu);
> -
> - if (!skip_tlb_flush)
> + if (!skip_tlb_flush) {
> + kvm_mmu_sync_roots(vcpu);
> kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
> + }
> return 0;
> }
>
> --
> 2.18.0.rc1.242.g61856ae69a-goog
>
