From: Paolo Bonzini pbonzini@redhat.com
[ 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@redhat.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- 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