Re: [PATCH v2] KVM: x86/pt: Ignore all unknown Intel PT capabilities

[Like Xu]

On 11/1/2022 3:59 pm, Xiaoyao Li wrote:
> > +#define GUEST_SUPPORTED_CPUID_14_EBX    \
> > +    (BIT(0) | BIT(1) | BIT(2) | BIT(3) | BIT(4) | BIT(5))
> > +
> > +#define GUEST_SUPPORTED_CPUID_14_ECX    \
> > +    (BIT(0) | BIT(1) | BIT(2) | BIT(3) | BIT(31))
> > +
>
> I doubt BIT(3) of CPUID_14_ECX can be exposed to guest directly.
>
> It means "output to Trace Transport Subsystem Supported". If I understand 
> correctly, it at least needs passthrough of the said Transport Subsystem or 
> emulation of it.

I'm not surprised that we can route Intel Guest PT output to a platform-specific
trace endpoint (e.g., physical or emulated JTAG) as an MMIO debug port.