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Message-Id: <20210504171734.1434054-15-seanjc@google.com>
Date: Tue, 4 May 2021 10:17:33 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Paolo Bonzini <pbonzini@...hat.com>
Cc: Sean Christopherson <seanjc@...gle.com>,
Vitaly Kuznetsov <vkuznets@...hat.com>,
Wanpeng Li <wanpengli@...cent.com>,
Jim Mattson <jmattson@...gle.com>,
Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
linux-kernel@...r.kernel.org, Xiaoyao Li <xiaoyao.li@...el.com>,
Reiji Watanabe <reijiw@...gle.com>
Subject: [PATCH 14/15] KVM: x86: Tie Intel and AMD behavior for MSR_TSC_AUX to
guest CPU model
Squish the Intel and AMD emulation of MSR_TSC_AUX together and tie it to
the guest CPU model instead of the host CPU behavior. While not strictly
necessary to avoid guest breakage, emulating cross-vendor "architecture"
will provide consistent behavior for the guest, e.g. WRMSR fault behavior
won't change if the vCPU is migrated to a host with divergent behavior.
Note, the "new" kvm_is_supported_user_return_msr() checks do not add new
functionality on either SVM or VMX. On SVM, the equivalent was
"tsc_aux_uret_slot < 0", and on VMX the check was buried in the
vmx_find_uret_msr() call at the find_uret_msr label.
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
arch/x86/include/asm/kvm_host.h | 5 +++++
arch/x86/kvm/svm/svm.c | 24 ----------------------
arch/x86/kvm/vmx/vmx.c | 15 --------------
arch/x86/kvm/x86.c | 36 +++++++++++++++++++++++++++++++++
4 files changed, 41 insertions(+), 39 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index a4b912f7e427..00fb9efb9984 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1782,6 +1782,11 @@ int kvm_add_user_return_msr(u32 msr);
int kvm_find_user_return_msr(u32 msr);
int kvm_set_user_return_msr(unsigned index, u64 val, u64 mask);
+static inline bool kvm_is_supported_user_return_msr(u32 msr)
+{
+ return kvm_find_user_return_msr(msr) >= 0;
+}
+
u64 kvm_scale_tsc(struct kvm_vcpu *vcpu, u64 tsc);
u64 kvm_read_l1_tsc(struct kvm_vcpu *vcpu, u64 host_tsc);
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index de921935e8de..6c7c6a303cc5 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -2663,12 +2663,6 @@ static int svm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
msr_info->data |= (u64)svm->sysenter_esp_hi << 32;
break;
case MSR_TSC_AUX:
- if (tsc_aux_uret_slot < 0)
- return 1;
- if (!msr_info->host_initiated &&
- !guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP) &&
- !guest_cpuid_has(vcpu, X86_FEATURE_RDPID))
- return 1;
msr_info->data = svm->tsc_aux;
break;
/*
@@ -2885,24 +2879,6 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
svm->sysenter_esp_hi = guest_cpuid_is_intel(vcpu) ? (data >> 32) : 0;
break;
case MSR_TSC_AUX:
- if (tsc_aux_uret_slot < 0)
- return 1;
-
- if (!msr->host_initiated &&
- !guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP) &&
- !guest_cpuid_has(vcpu, X86_FEATURE_RDPID))
- return 1;
-
- /*
- * Per Intel's SDM, bits 63:32 are reserved, but AMD's APM has
- * incomplete and conflicting architectural behavior. Current
- * AMD CPUs completely ignore bits 63:32, i.e. they aren't
- * reserved and always read as zeros. Emulate AMD CPU behavior
- * to avoid explosions if the vCPU is migrated from an AMD host
- * to an Intel host.
- */
- data = (u32)data;
-
/*
* TSC_AUX is usually changed only during boot and never read
* directly. Intercept TSC_AUX instead of exposing it to the
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 26f82f302391..d85ac5876982 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1981,12 +1981,6 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
else
msr_info->data = vmx->pt_desc.guest.addr_a[index / 2];
break;
- case MSR_TSC_AUX:
- if (!msr_info->host_initiated &&
- !guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP) &&
- !guest_cpuid_has(vcpu, X86_FEATURE_RDPID))
- return 1;
- goto find_uret_msr;
case MSR_IA32_DEBUGCTLMSR:
msr_info->data = vmcs_read64(GUEST_IA32_DEBUGCTL);
break;
@@ -2302,15 +2296,6 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
else
vmx->pt_desc.guest.addr_a[index / 2] = data;
break;
- case MSR_TSC_AUX:
- if (!msr_info->host_initiated &&
- !guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP) &&
- !guest_cpuid_has(vcpu, X86_FEATURE_RDPID))
- return 1;
- /* Check reserved bit, higher 32 bits should be zero */
- if ((data >> 32) != 0)
- return 1;
- goto find_uret_msr;
case MSR_IA32_PERF_CAPABILITIES:
if (data && !vcpu_to_pmu(vcpu)->version)
return 1;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index adca491d3b4b..896127ea4d4f 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1642,6 +1642,30 @@ static int __kvm_set_msr(struct kvm_vcpu *vcpu, u32 index, u64 data,
* invokes 64-bit SYSENTER.
*/
data = get_canonical(data, vcpu_virt_addr_bits(vcpu));
+ break;
+ case MSR_TSC_AUX:
+ if (!kvm_is_supported_user_return_msr(MSR_TSC_AUX))
+ return 1;
+
+ if (!host_initiated &&
+ !guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP) &&
+ !guest_cpuid_has(vcpu, X86_FEATURE_RDPID))
+ return 1;
+
+ /*
+ * Per Intel's SDM, bits 63:32 are reserved, but AMD's APM has
+ * incomplete and conflicting architectural behavior. Current
+ * AMD CPUs completely ignore bits 63:32, i.e. they aren't
+ * reserved and always read as zeros. Enforce Intel's reserved
+ * bits check if and only if the guest CPU is Intel, and clear
+ * the bits in all other cases. This ensures cross-vendor
+ * migration will provide consistent behavior for the guest.
+ */
+ if (guest_cpuid_is_intel(vcpu) && (data >> 32) != 0)
+ return 1;
+
+ data = (u32)data;
+ break;
}
msr.data = data;
@@ -1678,6 +1702,18 @@ int __kvm_get_msr(struct kvm_vcpu *vcpu, u32 index, u64 *data,
if (!host_initiated && !kvm_msr_allowed(vcpu, index, KVM_MSR_FILTER_READ))
return KVM_MSR_RET_FILTERED;
+ switch (index) {
+ case MSR_TSC_AUX:
+ if (!kvm_is_supported_user_return_msr(MSR_TSC_AUX))
+ return 1;
+
+ if (!host_initiated &&
+ !guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP) &&
+ !guest_cpuid_has(vcpu, X86_FEATURE_RDPID))
+ return 1;
+ break;
+ }
+
msr.index = index;
msr.host_initiated = host_initiated;
--
2.31.1.527.g47e6f16901-goog
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