[v3] KVM: x86/mmu: refine memtype related mmu zap

[PATCH v3 04/11] KVM: x86/mmu: Use KVM honors guest MTRRs helper when update mtrr

Posted by Yan Zhao 2 years, 7 months ago

Call helper to check if guest MTRRs are honored by KVM MMU before
calculation and zapping.
Guest MTRRs only affect TDP memtypes when TDP honors guest MTRRs, there's
no meaning to do the calculation and zapping otherwise.

Suggested-by: Chao Gao <chao.gao@intel.com>
Suggested-by: Sean Christopherson <seanjc@google.com>
Cc: Kai Huang <kai.huang@intel.com>
Signed-off-by: Yan Zhao <yan.y.zhao@intel.com>
---
 arch/x86/kvm/mtrr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/mtrr.c b/arch/x86/kvm/mtrr.c
index 3eb6e7f47e96..a67c28a56417 100644
--- a/arch/x86/kvm/mtrr.c
+++ b/arch/x86/kvm/mtrr.c
@@ -320,7 +320,7 @@ static void update_mtrr(struct kvm_vcpu *vcpu, u32 msr)
 	struct kvm_mtrr *mtrr_state = &vcpu->arch.mtrr_state;
 	gfn_t start, end;
 
-	if (!tdp_enabled || !kvm_arch_has_noncoherent_dma(vcpu->kvm))
+	if (!kvm_mmu_honors_guest_mtrrs(vcpu->kvm))
 		return;
 
 	if (!mtrr_is_enabled(mtrr_state) && msr != MSR_MTRRdefType)
-- 
2.17.1

Re: [PATCH v3 04/11] KVM: x86/mmu: Use KVM honors guest MTRRs helper when update mtrr

Posted by Sean Christopherson 2 years, 7 months ago

On Fri, Jun 16, 2023, Yan Zhao wrote:
> Call helper to check if guest MTRRs are honored by KVM MMU before
> calculation and zapping.

Same comment here about stating the effect, not the literal code change.

> Guest MTRRs only affect TDP memtypes when TDP honors guest MTRRs, there's
> no meaning to do the calculation and zapping otherwise.