LGTM.
Reviewed-By: Jon Cargille <jcargill@xxxxxxxxxx>
On Tue, Jun 23, 2020 at 12:40 PM Sean Christopherson
<sean.j.christopherson@xxxxxxxxx> wrote:
>
> Skip the unsync checks and the write flooding clearing for fully direct
> MMUs, which are guaranteed to not have unsync'd or indirect pages (write
> flooding detection only applies to indirect pages). For TDP, this
> avoids unnecessary memory reads and writes, and for the write flooding
> count will also avoid dirtying a cache line (unsync_child_bitmap itself
> consumes a cache line, i.e. write_flooding_count is guaranteed to be in
> a different cache line than parent_ptes).
>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> ---
> arch/x86/kvm/mmu/mmu.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 67f8f82e9783..c568a5c55276 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -2475,6 +2475,7 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
> int direct,
> unsigned int access)
> {
> + bool direct_mmu = vcpu->arch.mmu->direct_map;
> union kvm_mmu_page_role role;
> struct hlist_head *sp_list;
> unsigned quadrant;
> @@ -2490,8 +2491,7 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
> if (role.direct)
> role.gpte_is_8_bytes = true;
> role.access = access;
> - if (!vcpu->arch.mmu->direct_map
> - && vcpu->arch.mmu->root_level <= PT32_ROOT_LEVEL) {
> + if (!direct_mmu && vcpu->arch.mmu->root_level <= PT32_ROOT_LEVEL) {
> quadrant = gaddr >> (PAGE_SHIFT + (PT64_PT_BITS * level));
> quadrant &= (1 << ((PT32_PT_BITS - PT64_PT_BITS) * level)) - 1;
> role.quadrant = quadrant;
> @@ -2510,6 +2510,9 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
> if (sp->role.word != role.word)
> continue;
>
> + if (direct_mmu)
> + goto trace_get_page;
> +
> if (sp->unsync) {
> /* The page is good, but __kvm_sync_page might still end
> * up zapping it. If so, break in order to rebuild it.
> @@ -2525,6 +2528,8 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
> kvm_make_request(KVM_REQ_TLB_FLUSH_CURRENT, vcpu);
>
> __clear_sp_write_flooding_count(sp);
> +
> +trace_get_page:
> trace_kvm_mmu_get_page(sp, false);
> goto out;
> }
> --
> 2.26.0
>
