On Thu, Nov 03, 2022, Paolo Bonzini wrote:
> On 11/3/22 00:19, Sean Christopherson wrote:
> > + if (!boot_cpu_has(X86_FEATURE_MSR_IA32_FEAT_CTL) ||
> > + !boot_cpu_has(X86_FEATURE_VMX)) {
> > + pr_err("VMX not enabled in MSR_IA32_FEAT_CTL\n");
> > + return false;
>
> I think the reference to the BIOS should remain in these messages and in
> svm.c (even though these days it's much less common for vendors to default
> to disabled virtualization in the system setup).
Ya, I'll figure out a way to mention BIOS/firmware.
> The check for X86_FEATURE_MSR_IA32_FEAT_CTL is not needed because
> init_ia32_feat_ctl() will clear X86_FEATURE_VMX if the rdmsr fail (and not
> set X86_FEATURE_MSR_IA32_FEAT_CTL).
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.
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