Re: [PATCH v7 05/13] perf/x86/intel/pt: Introduce a new function to get capability of Intel PT

[Paolo Bonzini]

On 03/05/2018 14:13, Alexander Shishkin wrote:
>>>> New function __pt_cap_get() will be invoked in KVM to check if a
>>>> specific capability is availiable in KVM guest.
>>>> Another function pt_cap_get() can only check the hardware capabilities
>>>> but this may different with KVM guest because some features may not be
>>>> exposed to guest.
>>> Do we really need both in KVM?
>> Yes, KVM need get host capability to estimate if can expose this feature
>> to guest
> Can you elaborate on this, what information do we need besides
> MSR_IA32_VMX_MISC[14]?

It needs all the CPUID data, and it's nice to query it in a more
manageable form than with bit shifts.

Paolo