linux-kernel - [PATCH] KVM: x86: fix initial PAT value

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Date:	Mon, 27 Apr 2015 15:11:25 +0200
From:	Radim Krčmář <rkrcmar@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>
Subject: [PATCH] KVM: x86: fix initial PAT value

PAT should be 0007_0406_0007_0406h on RESET and not modified on INIT.
VMX used a wrong value (host's PAT) and while SVM used the right one,
it never got to arch.pat.

This is not an issue with QEMU as it will force the correct value.

Signed-off-by: Radim Krčmář <rkrcmar@...hat.com>
---
 arch/x86/kvm/svm.c |  2 +-
 arch/x86/kvm/vmx.c | 12 ++----------
 arch/x86/kvm/x86.c |  2 ++
 arch/x86/kvm/x86.h |  2 ++
 4 files changed, 7 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index ce741b8650f6..9aceb4a8c147 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1176,7 +1176,7 @@ static void init_vmcb(struct vcpu_svm *svm)
 		clr_exception_intercept(svm, PF_VECTOR);
 		clr_cr_intercept(svm, INTERCEPT_CR3_READ);
 		clr_cr_intercept(svm, INTERCEPT_CR3_WRITE);
-		save->g_pat = 0x0007040600070406ULL;
+		save->g_pat = svm->vcpu.arch.pat;
 		save->cr3 = 0;
 		save->cr4 = 0;
 	}
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index f7b61687bd79..62459382d305 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -4667,16 +4667,8 @@ static int vmx_vcpu_setup(struct vcpu_vmx *vmx)
 	vmcs_write32(VM_ENTRY_MSR_LOAD_COUNT, 0);
 	vmcs_write64(VM_ENTRY_MSR_LOAD_ADDR, __pa(vmx->msr_autoload.guest));
 
-	if (vmcs_config.vmentry_ctrl & VM_ENTRY_LOAD_IA32_PAT) {
-		u32 msr_low, msr_high;
-		u64 host_pat;
-		rdmsr(MSR_IA32_CR_PAT, msr_low, msr_high);
-		host_pat = msr_low | ((u64) msr_high << 32);
-		/* Write the default value follow host pat */
-		vmcs_write64(GUEST_IA32_PAT, host_pat);
-		/* Keep arch.pat sync with GUEST_IA32_PAT */
-		vmx->vcpu.arch.pat = host_pat;
-	}
+	if (vmcs_config.vmentry_ctrl & VM_ENTRY_LOAD_IA32_PAT)
+		vmcs_write64(GUEST_IA32_PAT, vmx->vcpu.arch.pat);
 
 	for (i = 0; i < ARRAY_SIZE(vmx_msr_index); ++i) {
 		u32 index = vmx_msr_index[i];
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c73efcd03e29..a20898f9e43a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7363,6 +7363,8 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
 
 	vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu);
 
+	vcpu->arch.pat = MSR_IA32_CR_PAT_DEFAULT;
+
 	kvm_async_pf_hash_reset(vcpu);
 	kvm_pmu_init(vcpu);
 
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index f5fef1868096..01a1d011e073 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -4,6 +4,8 @@
 #include <linux/kvm_host.h>
 #include "kvm_cache_regs.h"
 
+#define MSR_IA32_CR_PAT_DEFAULT  0x0007040600070406ULL
+
 static inline void kvm_clear_exception_queue(struct kvm_vcpu *vcpu)
 {
 	vcpu->arch.exception.pending = false;
-- 
2.3.6

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