From: Paolo Bonzini <pbonzini@xxxxxxxxxx>
[ Upstream commit 6441fa6178f5456d1d4b512c08798888f99db185 ]
If the guest is configured to have SPEC_CTRL but the host does not
(which is a nonsensical configuration but these are not explicitly
forbidden) then a host-initiated MSR write can write vmx->spec_ctrl
(respectively svm->spec_ctrl) and trigger a #GP when KVM tries to
restore the host value of the MSR. Add a more comprehensive check
for valid bits of SPEC_CTRL, covering host CPUID flags and,
since we are at it and it is more correct that way, guest CPUID
flags too.
For AMD, remove the unnecessary is_guest_mode check around setting
the MSR interception bitmap, so that the code looks the same as
for Intel.
Cc: Jim Mattson <jmattson@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
arch/x86/kvm/svm.c | 9 +++------
arch/x86/kvm/vmx/vmx.c | 7 +++----
arch/x86/kvm/x86.c | 22 ++++++++++++++++++++++
arch/x86/kvm/x86.h | 1 +
4 files changed, 29 insertions(+), 10 deletions(-)
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index c79c1a07f44b9..72bf1d8175ac2 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -4322,12 +4322,10 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
!guest_cpuid_has(vcpu, X86_FEATURE_AMD_SSBD))
return 1;
- /* The STIBP bit doesn't fault even if it's not advertised */
- if (data & ~(SPEC_CTRL_IBRS | SPEC_CTRL_STIBP | SPEC_CTRL_SSBD))
+ if (data & ~kvm_spec_ctrl_valid_bits(vcpu))
return 1;
svm->spec_ctrl = data;
-
if (!data)
break;
@@ -4351,13 +4349,12 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
if (data & ~PRED_CMD_IBPB)
return 1;
-
+ if (!boot_cpu_has(X86_FEATURE_AMD_IBPB))
+ return 1;
if (!data)
break;
wrmsrl(MSR_IA32_PRED_CMD, PRED_CMD_IBPB);
- if (is_guest_mode(vcpu))
- break;
set_msr_interception(svm->msrpm, MSR_IA32_PRED_CMD, 0, 1);
break;
case MSR_AMD64_VIRT_SPEC_CTRL:
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 2a1ed3aae100e..8450fce70bd96 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1974,12 +1974,10 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
!guest_cpuid_has(vcpu, X86_FEATURE_SPEC_CTRL))
return 1;
- /* The STIBP bit doesn't fault even if it's not advertised */
- if (data & ~(SPEC_CTRL_IBRS | SPEC_CTRL_STIBP | SPEC_CTRL_SSBD))
+ if (data & ~kvm_spec_ctrl_valid_bits(vcpu))
return 1;
vmx->spec_ctrl = data;
-
if (!data)
break;
@@ -2006,7 +2004,8 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
if (data & ~PRED_CMD_IBPB)
return 1;
-
+ if (!boot_cpu_has(X86_FEATURE_SPEC_CTRL))
+ return 1;
if (!data)
break;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index b7f86acb8c911..72990c3c6faf7 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10369,6 +10369,28 @@ bool kvm_arch_no_poll(struct kvm_vcpu *vcpu)
}
EXPORT_SYMBOL_GPL(kvm_arch_no_poll);
+u64 kvm_spec_ctrl_valid_bits(struct kvm_vcpu *vcpu)
+{
+ uint64_t bits = SPEC_CTRL_IBRS | SPEC_CTRL_STIBP | SPEC_CTRL_SSBD;
+
+ /* The STIBP bit doesn't fault even if it's not advertised */
+ if (!guest_cpuid_has(vcpu, X86_FEATURE_SPEC_CTRL) &&
+ !guest_cpuid_has(vcpu, X86_FEATURE_AMD_IBRS))
+ bits &= ~(SPEC_CTRL_IBRS | SPEC_CTRL_STIBP);
+ if (!boot_cpu_has(X86_FEATURE_SPEC_CTRL) &&
+ !boot_cpu_has(X86_FEATURE_AMD_IBRS))
+ bits &= ~(SPEC_CTRL_IBRS | SPEC_CTRL_STIBP);
+
+ if (!guest_cpuid_has(vcpu, X86_FEATURE_SPEC_CTRL_SSBD) &&
+ !guest_cpuid_has(vcpu, X86_FEATURE_AMD_SSBD))
+ bits &= ~SPEC_CTRL_SSBD;
+ if (!boot_cpu_has(X86_FEATURE_SPEC_CTRL_SSBD) &&
+ !boot_cpu_has(X86_FEATURE_AMD_SSBD))
+ bits &= ~SPEC_CTRL_SSBD;
+
+ return bits;
+}
+EXPORT_SYMBOL_GPL(kvm_spec_ctrl_valid_bits);
EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_exit);
EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_fast_mmio);
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index de6b55484876a..301286d924320 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -368,5 +368,6 @@ static inline bool kvm_pat_valid(u64 data)
void kvm_load_guest_xcr0(struct kvm_vcpu *vcpu);
void kvm_put_guest_xcr0(struct kvm_vcpu *vcpu);
+u64 kvm_spec_ctrl_valid_bits(struct kvm_vcpu *vcpu);
#endif
--
2.27.0
