Messages in this thread | | | Date | Thu, 16 Dec 2021 11:24:23 +0100 | Subject | Re: [patch 5/6] x86/fpu: Provide fpu_update_guest_xcr0/xfd() | From | Paolo Bonzini <> |
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On 12/16/21 11:21, Tian, Kevin wrote: >> 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.
Right, this is a generic /dev/kvm ioctl therefore it has to check the process state.
> 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?
You can document it under the KVM_GET_SUPPORTED_CPUID ioctl.
Paolo
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