linux-kernel - [PATCH v4 06/12] KVM: x86/mmu: move TDP zaps from guest MTRRs update to CR0.CD toggling

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Message-Id: <20230714065256.20492-1-yan.y.zhao@intel.com>
Date:   Fri, 14 Jul 2023 14:52:56 +0800
From:   Yan Zhao <yan.y.zhao@...el.com>
To:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     pbonzini@...hat.com, seanjc@...gle.com, chao.gao@...el.com,
        kai.huang@...el.com, robert.hoo.linux@...il.com,
        yuan.yao@...ux.intel.com, Yan Zhao <yan.y.zhao@...el.com>
Subject: [PATCH v4 06/12] KVM: x86/mmu: move TDP zaps from guest MTRRs update to CR0.CD toggling

If guest MTRRs are honored, always zap TDP when CR0.CD toggles and don't do
it if guest MTRRs are updated under CR0.CD=1.

This is because CR0.CD=1 takes precedence over guest MTRRs to decide TDP
memory types, TDP memtypes are not changed if guest MTRRs update under
CR0.CD=1.

Instead, always do the TDP zapping when CR0.CD toggles, because even with
the quirk KVM_X86_QUIRK_CD_NW_CLEARED, TDP memory types may change after
guest CR0.CD toggles.

Suggested-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Yan Zhao <yan.y.zhao@...el.com>
---
 arch/x86/kvm/mtrr.c | 3 +++
 arch/x86/kvm/x86.c  | 3 +--
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/mtrr.c b/arch/x86/kvm/mtrr.c
index a67c28a56417..3ce58734ad22 100644
--- a/arch/x86/kvm/mtrr.c
+++ b/arch/x86/kvm/mtrr.c
@@ -323,6 +323,9 @@ static void update_mtrr(struct kvm_vcpu *vcpu, u32 msr)
 	if (!kvm_mmu_honors_guest_mtrrs(vcpu->kvm))
 		return;
 
+	if (kvm_is_cr0_bit_set(vcpu, X86_CR0_CD))
+		return;
+
 	if (!mtrr_is_enabled(mtrr_state) && msr != MSR_MTRRdefType)
 		return;
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index ac9548efa76f..32cc8bfaa5f1 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -942,8 +942,7 @@ void kvm_post_set_cr0(struct kvm_vcpu *vcpu, unsigned long old_cr0, unsigned lon
 		kvm_mmu_reset_context(vcpu);
 
 	if (((cr0 ^ old_cr0) & X86_CR0_CD) &&
-	    kvm_mmu_honors_guest_mtrrs(vcpu->kvm) &&
-	    !kvm_check_has_quirk(vcpu->kvm, KVM_X86_QUIRK_CD_NW_CLEARED))
+	    kvm_mmu_honors_guest_mtrrs(vcpu->kvm))
 		kvm_zap_gfn_range(vcpu->kvm, 0, ~0ULL);
 }
 EXPORT_SYMBOL_GPL(kvm_post_set_cr0);
-- 
2.17.1