Messages in this thread | | | Subject | Re: [PATCH] KVM: X86: Expose KVM_HINTS_REALTIME in KVM_GET_SUPPORTED_CPUID | From | Paolo Bonzini <> | Date | Thu, 22 Oct 2020 16:44:52 +0200 |
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On 22/10/20 16:28, Xiaoyao Li wrote: > On 10/22/2020 10:06 PM, Paolo Bonzini wrote: >> On 22/10/20 15:31, Xiaoyao Li wrote: >>>> >>>> It's common for userspace to copy all supported CPUID bits to >>>> KVM_SET_CPUID2, I don't think this is the right behavior for >>>> KVM_HINTS_REALTIME. >>> >>> It reminds of X86_FEATURE_WAITPKG, which is added to supported CPUID >>> recently as a fix but QEMU exposes it to guest only when "-overcommit >>> cpu-pm" >> >> WAITPKG is not included in KVM_GET_SUPPORTED_CPUID either. QEMU detects >> it through the MSR_IA32_UMWAIT register. > > Doesn't 0abcc8f65cc2 ("KVM: VMX: enable X86_FEATURE_WAITPKG in KVM > capabilities") add WAITPKG to KVM_GET_SUPPORTED_CPUID?
You're right, I shouldn't have checked only cpuid.c. :)
Still I think WAITPKG is different, because it's only for userspace and it's always possible for userspace to do "for(;;)" and burn CPU. KVM_HINTS_REALTIME is more similar to MONITOR, which is not set.
Paolo
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