On Tue, Jan 26, 2021, Ben Gardon wrote:

On Wed, Jan 20, 2021 at 4:56 PM Sean Christopherson [off-list ref] wrote:

quoted

On Tue, Jan 12, 2021, Ben Gardon wrote:

quoted

Make the last few changes necessary to enable the TDP MMU to handle page
faults in parallel while holding the mmu_lock in read mode.

Reviewed-by: Peter Feiner <redacted>

Signed-off-by: Ben Gardon <redacted>
---
 arch/x86/kvm/mmu/mmu.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 280d7cd6f94b..fa111ceb67d4 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c

@@ -3724,7 +3724,12 @@ static int direct_page_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code,
              return r;

      r = RET_PF_RETRY;
-     kvm_mmu_lock(vcpu->kvm);
+
+     if (is_tdp_mmu_root(vcpu->kvm, vcpu->arch.mmu->root_hpa))

Off topic, what do you think about rewriting is_tdp_mmu_root() to be both more
performant and self-documenting as to when is_tdp_mmu_root() !=
kvm->arch.tdp_mmu_enabled?  E.g. key off is_guest_mode() and then do a thorough
audit/check when CONFIG_KVM_MMU_AUDIT=y?

#ifdef CONFIG_KVM_MMU_AUDIT
bool is_tdp_mmu_root(struct kvm *kvm, hpa_t hpa)
{
        struct kvm_mmu_page *sp;

        if (!kvm->arch.tdp_mmu_enabled)
                return false;
        if (WARN_ON(!VALID_PAGE(hpa)))
                return false;

        sp = to_shadow_page(hpa);
        if (WARN_ON(!sp))
                return false;

        return sp->tdp_mmu_page && sp->root_count;
}
#endif

bool is_tdp_mmu(struct kvm_vcpu *vcpu)
{
        bool is_tdp_mmu = kvm->arch.tdp_mmu_enabled && !is_guest_mode(vcpu);

#ifdef CONFIG_KVM_MMU_AUDIT
        WARN_ON(is_tdp_mmu != is_tdp_mmu_root(vcpu->kvm, vcpu->arch.mmu->root_hpa));
#endif
        return is_tdp_mmu;
}

Great suggestions. In the interest of keeping this (already enormous)
series small, I'm inclined to make those changes in a future series if
that's alright with you.

Yep, definitely a different series.