[PATCH 8/9] KVM: MMU: fix MTRR update

[guangrong.xiao@linux.intel.com]

From: Xiao Guangrong <guangrong.xiao@linux.intel.com>

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 fixes this issue by dropping all the spte in the gfn range which is
being updated by MTRR

Signed-off-by: Xiao Guangrong <guangrong.xiao@linux.intel.com>
---
 arch/x86/include/asm/kvm_host.h |  2 ++
 arch/x86/kvm/svm.c              |  5 ++++
 arch/x86/kvm/vmx.c              | 58 +++++++++++++++++++++++++++++++++++++++++
 arch/x86/kvm/x86.c              |  2 +-
 4 files changed, 66 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index dea2e7e..ae9528d 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -778,6 +778,8 @@ struct kvm_x86_ops {
 	int (*set_tss_addr)(struct kvm *kvm, unsigned int addr);
 	int (*get_tdp_level)(void);
 	u64 (*get_mt_mask)(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio);
+	void (*set_msr_mtrr)(struct kvm_vcpu *vcpu, u32 msr);
+
 	int (*get_lpage_level)(void);
 	bool (*rdtscp_supported)(void);
 	bool (*invpcid_supported)(void);
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index ce741b8..c33573c 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -4078,6 +4078,10 @@ static u64 svm_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio)
 	return 0;
 }
 
+static void svm_set_msr_mtrr(struct kvm_vcpu *vcpu, u32 msr)
+{
+}
+
 static void svm_cpuid_update(struct kvm_vcpu *vcpu)
 {
 }
@@ -4410,6 +4414,7 @@ static struct kvm_x86_ops svm_x86_ops = {
 	.set_tss_addr = svm_set_tss_addr,
 	.get_tdp_level = get_npt_level,
 	.get_mt_mask = svm_get_mt_mask,
+	.set_msr_mtrr = svm_set_msr_mtrr,
 
 	.get_exit_info = svm_get_exit_info,
 
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index f7b6168..fcd0001 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -8505,6 +8505,63 @@ static u64 vmx_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio)
 	return ret;
 }
 
+static void vmx_set_msr_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 || !enable_ept ||
+	      !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 vmx_get_lpage_level(void)
 {
 	if (enable_ept && !cpu_has_vmx_ept_1g_page())
@@ -10218,6 +10275,7 @@ static struct kvm_x86_ops vmx_x86_ops = {
 	.set_tss_addr = vmx_set_tss_addr,
 	.get_tdp_level = get_ept_level,
 	.get_mt_mask = vmx_get_mt_mask,
+	.set_msr_mtrr = vmx_set_msr_mtrr,
 
 	.get_exit_info = vmx_get_exit_info,
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c73efcd..579c205 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1887,7 +1887,7 @@ static int set_msr_mtrr(struct kvm_vcpu *vcpu, u32 msr, u64 data)
 		*pt = data;
 	}
 
-	kvm_mmu_reset_context(vcpu);
+	kvm_x86_ops->set_msr_mtrr(vcpu, msr);
 	return 0;
 }
 
-- 
1.9.3