On Thu, Nov 03, 2022, Paolo Bonzini wrote:
> On 11/3/22 19:35, Sean Christopherson wrote:
> > It's technically required. IA32_FEAT_CTL and thus KVM_INTEL depends on any of
> > CPU_SUP_{INTEL,CENATUR,ZHAOXIN}, but init_ia32_feat_ctl() is invoked if and only
> > if the actual CPU type matches one of the aforementioned CPU_SUP_*.
> >
> > E.g. running a kernel built with
> >
> > CONFIG_CPU_SUP_INTEL=y
> > CONFIG_CPU_SUP_AMD=y
> > # CONFIG_CPU_SUP_HYGON is not set
> > # CONFIG_CPU_SUP_CENTAUR is not set
> > # CONFIG_CPU_SUP_ZHAOXIN is not set
> >
> > on a Cenatur or Zhaoxin CPU will leave X86_FEATURE_VMX set but not set
> > X86_FEATURE_MSR_IA32_FEAT_CTL. If VMX isn't enabled in MSR_IA32_FEAT_CTL, KVM
> > will get unexpected #UDs when trying to enable VMX.
>
> Oh, I see. Perhaps X86_FEATURE_VMX and X86_FEATURE_SGX should be moved to
> one of the software words instead of using cpuid. Nothing that you should
> care about for this series though.
Or maybe something like this?
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 3e508f239098..ebe617ab0b37 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -191,6 +191,8 @@ static void default_init(struct cpuinfo_x86 *c)
strcpy(c->x86_model_id, "386");
}
#endif
+
+ clear_cpu_cap(c, X86_FEATURE_MSR_IA32_FEAT_CTL);
}
static const struct cpu_dev default_cpu = {
diff --git a/arch/x86/kernel/cpu/cpuid-deps.c b/arch/x86/kernel/cpu/cpuid-deps.c
index c881bcafba7d..3a7ae67f5a5e 100644
--- a/arch/x86/kernel/cpu/cpuid-deps.c
+++ b/arch/x86/kernel/cpu/cpuid-deps.c
@@ -72,6 +72,8 @@ static const struct cpuid_dep cpuid_deps[] = {
{ X86_FEATURE_AVX512_FP16, X86_FEATURE_AVX512BW },
{ X86_FEATURE_ENQCMD, X86_FEATURE_XSAVES },
{ X86_FEATURE_PER_THREAD_MBA, X86_FEATURE_MBA },
+ { X86_FEATURE_VMX, X86_FEATURE_MSR_IA32_FEAT_CTL },
+ { X86_FEATURE_SGX, X86_FEATURE_MSR_IA32_FEAT_CTL },
{ X86_FEATURE_SGX_LC, X86_FEATURE_SGX },
{ X86_FEATURE_SGX1, X86_FEATURE_SGX },
{ X86_FEATURE_SGX2, X86_FEATURE_SGX1 },
