Messages in this thread | | | From | "Tian, Kevin" <> | Subject | RE: [patch 5/6] x86/fpu: Provide fpu_update_guest_xcr0/xfd() | Date | Thu, 16 Dec 2021 10:21:48 +0000 |
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> From: Paolo Bonzini > Sent: Wednesday, December 15, 2021 6:41 PM > > There's also another important thing that hasn't been mentioned so far: > KVM_GET_SUPPORTED_CPUID should _not_ include the dynamic bits in > CPUID[0xD] if they have not been requested with prctl. It's okay to > return the AMX bit, but not the bit in CPUID[0xD].
There is no vcpu in this ioctl, thus we cannot check vcpu->arch.guest_fpu.perm.
This then requires exposing xstate_get_guest_group_perm() to KVM. Thomas, are you OK with this change given Paolo's ask? v1 included this change but it was not necessary at the moment:
https://lore.kernel.org/lkml/87lf0ot50q.ffs@tglx/
and Paolo, do we want to document that prctl() must be done before calling KVM_GET_SUPPORTED_CPUID? If yes, where is the proper location?
Thanks Kevin
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