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

Yan Zhao
2023-05-09T14:15:32Z

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@intel.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