| Message ID | 20220203010051.2813563-2-dmatlack@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Extend Eager Page Splitting to the shadow MMU | expand |
On Thu, Feb 03, 2022, David Matlack wrote: > Commit fb58a9c345f6 ("KVM: x86/mmu: Optimize MMU page cache lookup for > fully direct MMUs") skipped the unsync checks and write flood clearing > for full direct MMUs. We can extend this further and skip the checks for > all direct shadow pages. Direct shadow pages are never marked unsynced > or have a non-zero write-flooding count. > > No functional change intended. > > Signed-off-by: David Matlack <dmatlack@google.com> > --- Reviewed-by: Sean Christopherson <seanjc@google.com> > arch/x86/kvm/mmu/mmu.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > index 296f8723f9ae..6ca38277f2ab 100644 > --- a/arch/x86/kvm/mmu/mmu.c > +++ b/arch/x86/kvm/mmu/mmu.c > @@ -2052,7 +2052,6 @@ 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; > @@ -2093,7 +2092,8 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, > continue; > } > > - if (direct_mmu) > + /* unsync and write-flooding only apply to indirect SPs. */ > + if (sp->role.direct) Because I spent waaaay too much time over-analyzing this... checking sp->role.direct actually generates better code than check @direct. Because of regsiter pressure, direct has to get shoved onto the stack and then pulled back off. Not that it matters, at all, because this code runs exactly once... > goto trace_get_page; > > if (sp->unsync) { > -- > 2.35.0.rc2.247.g8bbb082509-goog >
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 296f8723f9ae..6ca38277f2ab 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -2052,7 +2052,6 @@ 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; @@ -2093,7 +2092,8 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, continue; } - if (direct_mmu) + /* unsync and write-flooding only apply to indirect SPs. */ + if (sp->role.direct) goto trace_get_page; if (sp->unsync) {
Commit fb58a9c345f6 ("KVM: x86/mmu: Optimize MMU page cache lookup for fully direct MMUs") skipped the unsync checks and write flood clearing for full direct MMUs. We can extend this further and skip the checks for all direct shadow pages. Direct shadow pages are never marked unsynced or have a non-zero write-flooding count. No functional change intended. Signed-off-by: David Matlack <dmatlack@google.com> --- arch/x86/kvm/mmu/mmu.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)