KVM: MMU: fix MTRR update

Currently, whenever guest MTRR registers are changed
kvm_mmu_reset_context is called to switch to the new root shadow page
table, however, it's useless since:
1) the cache type is not cached into shadow page's attribute so that
   the original root shadow page will be reused

2) the cache type is set on the last spte, that means we should sync
   the last sptes when MTRR is changed

This patch fixs this issue by drop all the spte in the gfn range which
is being updated by MTRR

Signed-off-by: Xiao Guangrong <guangrong.xiao@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 58 insertions, 1 deletions

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index cde5d614ff0a..bbe184f07bf9 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1852,6 +1852,63 @@ bool kvm_mtrr_valid(struct kvm_vcpu *vcpu, u32 msr, u64 data)
 }
 EXPORT_SYMBOL_GPL(kvm_mtrr_valid);
 
+static void update_mtrr(struct kvm_vcpu *vcpu, u32 msr)
+{
+	struct mtrr_state_type *mtrr_state = &vcpu->arch.mtrr_state;
+	unsigned char mtrr_enabled = mtrr_state->enabled;
+	gfn_t start, end, mask;
+	int index;
+	bool is_fixed = true;
+
+	if (msr == MSR_IA32_CR_PAT || !tdp_enabled ||
+	      !kvm_arch_has_noncoherent_dma(vcpu->kvm))
+		return;
+
+	if (!(mtrr_enabled & 0x2) && msr != MSR_MTRRdefType)
+		return;
+
+	switch (msr) {
+	case MSR_MTRRfix64K_00000:
+		start = 0x0;
+		end = 0x80000;
+		break;
+	case MSR_MTRRfix16K_80000:
+		start = 0x80000;
+		end = 0xa0000;
+		break;
+	case MSR_MTRRfix16K_A0000:
+		start = 0xa0000;
+		end = 0xc0000;
+		break;
+	case MSR_MTRRfix4K_C0000 ... MSR_MTRRfix4K_F8000:
+		index = msr - MSR_MTRRfix4K_C0000;
+		start = 0xc0000 + index * (32 << 10);
+		end = start + (32 << 10);
+		break;
+	case MSR_MTRRdefType:
+		is_fixed = false;
+		start = 0x0;
+		end = ~0ULL;
+		break;
+	default:
+		/* variable range MTRRs. */
+		is_fixed = false;
+		index = (msr - 0x200) / 2;
+		start = (((u64)mtrr_state->var_ranges[index].base_hi) << 32) +
+		       (mtrr_state->var_ranges[index].base_lo & PAGE_MASK);
+		mask = (((u64)mtrr_state->var_ranges[index].mask_hi) << 32) +
+		       (mtrr_state->var_ranges[index].mask_lo & PAGE_MASK);
+		mask |= ~0ULL << cpuid_maxphyaddr(vcpu);
+
+		end = ((start & mask) | ~mask) + 1;
+	}
+
+	if (is_fixed && !(mtrr_enabled & 0x1))
+		return;
+
+	kvm_zap_gfn_range(vcpu->kvm, gpa_to_gfn(start), gpa_to_gfn(end));
+}
+
 static int set_msr_mtrr(struct kvm_vcpu *vcpu, u32 msr, u64 data)
 {
 	u64 *p = (u64 *)&vcpu->arch.mtrr_state.fixed_ranges;
@@ -1885,7 +1942,7 @@ static int set_msr_mtrr(struct kvm_vcpu *vcpu, u32 msr, u64 data)
 		*pt = data;
 	}
 
-	kvm_mmu_reset_context(vcpu);
+	update_mtrr(vcpu, msr);
 	return 0;
 }