linux-kernel - [PATCH v3 02/11] KVM: x86/mmu: Use KVM honors guest MTRRs helper in kvm_tdp_page

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Date:   Fri, 16 Jun 2023 10:34:35 +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,
        Yan Zhao <yan.y.zhao@...el.com>
Subject: [PATCH v3 02/11] KVM: x86/mmu: Use KVM honors guest MTRRs helper in kvm_tdp_page_fault()

Let kvm_tdp_page_fault() use helper function kvm_mmu_honors_guest_mtrrs()
to decide if it needs to consult guest MTRR to check GFN range consistency.

No functional change intended.

Suggested-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Yan Zhao <yan.y.zhao@...el.com>
---
 arch/x86/kvm/mmu/mmu.c | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index b4f89f015c37..7f52bbe013b3 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4536,16 +4536,9 @@ int kvm_tdp_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
 	/*
 	 * If the guest's MTRRs may be used to compute the "real" memtype,
 	 * restrict the mapping level to ensure KVM uses a consistent memtype
-	 * across the entire mapping.  If the host MTRRs are ignored by TDP
-	 * (shadow_memtype_mask is non-zero), and the VM has non-coherent DMA
-	 * (DMA doesn't snoop CPU caches), KVM's ABI is to honor the memtype
-	 * from the guest's MTRRs so that guest accesses to memory that is
-	 * DMA'd aren't cached against the guest's wishes.
-	 *
-	 * Note, KVM may still ultimately ignore guest MTRRs for certain PFNs,
-	 * e.g. KVM will force UC memtype for host MMIO.
+	 * across the entire mapping.
 	 */
-	if (shadow_memtype_mask && kvm_arch_has_noncoherent_dma(vcpu->kvm)) {
+	if (kvm_mmu_honors_guest_mtrrs(vcpu->kvm)) {
 		for ( ; fault->max_level > PG_LEVEL_4K; --fault->max_level) {
 			int page_num = KVM_PAGES_PER_HPAGE(fault->max_level);
 			gfn_t base = gfn_round_for_level(fault->gfn,
-- 
2.17.1