There are few cases when this function was creating a bogus #GP condition, for example case when and AMD host supports STIBP but doesn't support SSBD.
Follow the rules for AMD and Intel strictly instead. AMD #GP rules for IA32_SPEC_CTRL can be found here: https://bugzilla.kernel.org/show_bug.cgi?id=199889 Fixes: 6441fa6178f5 ("KVM: x86: avoid incorrect writes to host MSR_IA32_SPEC_CTRL") Signed-off-by: Maxim Levitsky <[email protected]> --- arch/x86/kvm/x86.c | 57 ++++++++++++++++++++++++++++++++++------------ 1 file changed, 42 insertions(+), 15 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 00c88c2f34e4..a6bed4670b7f 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -10670,27 +10670,54 @@ 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) + +static u64 kvm_spec_ctrl_valid_bits_host(void) +{ + uint64_t bits = 0; + + if (boot_cpu_has(X86_FEATURE_SPEC_CTRL)) + bits |= SPEC_CTRL_IBRS; + if (boot_cpu_has(X86_FEATURE_INTEL_STIBP)) + bits |= SPEC_CTRL_STIBP; + if (boot_cpu_has(X86_FEATURE_SPEC_CTRL_SSBD)) + bits |= SPEC_CTRL_SSBD; + + if (boot_cpu_has(X86_FEATURE_AMD_IBRS) || boot_cpu_has(X86_FEATURE_AMD_STIBP)) + bits |= SPEC_CTRL_STIBP | SPEC_CTRL_IBRS; + + if (boot_cpu_has(X86_FEATURE_AMD_SSBD)) + bits |= SPEC_CTRL_STIBP | SPEC_CTRL_IBRS | SPEC_CTRL_SSBD; + + return bits; +} + +static u64 kvm_spec_ctrl_valid_bits_guest(struct kvm_vcpu *vcpu) { - uint64_t bits = SPEC_CTRL_IBRS | SPEC_CTRL_STIBP | SPEC_CTRL_SSBD; + uint64_t bits = 0; - /* 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)) + bits |= SPEC_CTRL_IBRS; + if (guest_cpuid_has(vcpu, X86_FEATURE_INTEL_STIBP)) + bits |= SPEC_CTRL_STIBP; + if (guest_cpuid_has(vcpu, X86_FEATURE_SPEC_CTRL_SSBD)) + bits |= SPEC_CTRL_SSBD; - 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; + if (guest_cpuid_has(vcpu, X86_FEATURE_AMD_IBRS) || + guest_cpuid_has(vcpu, X86_FEATURE_AMD_STIBP)) + bits |= SPEC_CTRL_STIBP | SPEC_CTRL_IBRS; + if (guest_cpuid_has(vcpu, X86_FEATURE_AMD_SSBD)) + bits |= SPEC_CTRL_STIBP | SPEC_CTRL_IBRS | SPEC_CTRL_SSBD; return bits; } + +u64 kvm_spec_ctrl_valid_bits(struct kvm_vcpu *vcpu) +{ + return kvm_spec_ctrl_valid_bits_host() & + kvm_spec_ctrl_valid_bits_guest(vcpu); +} + + EXPORT_SYMBOL_GPL(kvm_spec_ctrl_valid_bits); EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_exit); -- 2.25.4
