Re: [PATCH] x86/fpu: Fix the os panic issue caused by the XGETBV instruction

[H. Peter Anvin]

On 1/17/25 14:10, Sean Christopherson wrote:
> > Note that XFD is already listed as dependent on XGETBV1.
> >
> > But I doubt the kernel needs to be resilient to deliberately misconfigured
> > or crazy virtual machine setups.
>
> I don't see anything in the SDM that suggests this is a misconfigured CPU.  Intel
> might not have plans to ship such CPUs, but AFAICT it's not a violation of the
> architecture as defined in the SDM.
>
> The SDM even explicitly says that protection keys can exist and be used without
> PKU state being supported in XSAVE at all, at which point assuming the existence
> of XGETBV1 is rather nonsensical.

Whether or not a combination is *possible* at all is totally separate 
from whether or not it is worth for Linux to support it. The CPUID 
dependency list exists for exactly that reason -- it defines *Linux 
policy* with regards to feature dependencies.

	-hpa