linux-kernel - [PATCH v2 1/6] KVM: x86/mmu: add a new mmu zap helper to indicate memtype changes

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Date:   Tue,  9 May 2023 21:50:06 +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,
        Yan Zhao <yan.y.zhao@...el.com>
Subject: [PATCH v2 1/6] KVM: x86/mmu: add a new mmu zap helper to indicate memtype changes

Add a helper to indicate that the kvm_zap_gfn_range() request is to update
memory type.

Then the zap can be avoided in cases:
1. TDP is not enabled.
2. EPT is not enabled.

This is because only memory type of EPT leaf entries are subjected to
change when noncoherent DMA/guest CR0.CD/guest MTRR settings change.

Signed-off-by: Yan Zhao <yan.y.zhao@...el.com>
---
 arch/x86/kvm/mmu.h     |  1 +
 arch/x86/kvm/mmu/mmu.c | 16 ++++++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index 92d5a1924fc1..a04577afbc71 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -236,6 +236,7 @@ static inline u8 permission_fault(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
 }
 
 void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end);
+void kvm_zap_gfn_for_memtype(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end);
 
 int kvm_arch_write_log_dirty(struct kvm_vcpu *vcpu);
 
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index c8961f45e3b1..2706754794d1 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -6272,6 +6272,22 @@ static bool kvm_rmap_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_e
 	return flush;
 }
 
+/*
+ * Invalidate (zap) TDP SPTEs that cover GFNs from gfn_start and up to gfn_end
+ * (not including it) for reason of memory type being updated.
+ */
+void kvm_zap_gfn_for_memtype(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end)
+{
+	/* Currently only memory type of EPT leaf entries are affected by
+	 * guest CR0.CD and guest MTRR.
+	 * So skip invalidation (zap) in other cases
+	 */
+	if (!shadow_memtype_mask)
+		return;
+
+	kvm_zap_gfn_range(kvm, gpa_to_gfn(0), gpa_to_gfn(~0ULL));
+}
+
 /*
  * Invalidate (zap) SPTEs that cover GFNs from gfn_start and up to gfn_end
  * (not including it)
-- 
2.17.1