Re: [patch 0/6] x86/fpu: Preparatory changes for guest AMX support

[Paolo Bonzini]

On 12/14/21 03:50, Thomas Gleixner wrote:
> The only remaining issue is the KVM XSTATE save/restore size checking which
> probably requires some FPU core assistance. But that requires some more
> thoughts vs. the IOCTL interface extension and once that is settled it
> needs to be solved in one go. But that's an orthogonal issue to the above.

That's not a big deal because KVM uses the uncompacted format.  So 
KVM_CHECK_EXTENSION and KVM_GET_XSAVE can just use CPUID to retrieve the 
size and uncompacted offset of the largest bit that is set in 
kvm_supported_xcr0, while KVM_SET_XSAVE can do the same with the largest 
bit that is set in the xstate_bv.

Paolo



> The series is also available from git:
>
>     git://git.kernel.org/pub/scm/linux/kernel/git/people/tglx/devel.git x86/fpu-kvm