From: Paolo Bonzini <pbonzini@redhat.com>
To: "Tian, Kevin" <kevin.tian@intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
"Wang, Wei W" <wei.w.wang@intel.com>,
"quintela@redhat.com" <quintela@redhat.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
Jing Liu <jing2.liu@linux.intel.com>,
"Zhong, Yang" <yang.zhong@intel.com>,
"x86@kernel.org" <x86@kernel.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>, "Christopherson,,
Sean" <seanjc@google.com>,
"Nakajima, Jun" <jun.nakajima@intel.com>,
"Zeng, Guang" <guang.zeng@intel.com>
Subject: Re: [patch 5/6] x86/fpu: Provide fpu_update_guest_xcr0/xfd()
Date: Thu, 16 Dec 2021 11:24:23 +0100 [thread overview]
Message-ID: <ffcea397-d66e-3ce0-41a4-0be07c7052c1@redhat.com> (raw)
In-Reply-To: <BN9PR11MB5276FE9D7F220C60DFB328428C779@BN9PR11MB5276.namprd11.prod.outlook.com>
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
next prev parent reply other threads:[~2021-12-16 10:24 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-14 2:50 [patch 0/6] x86/fpu: Preparatory changes for guest AMX support Thomas Gleixner
2021-12-14 2:50 ` [patch 1/6] x86/fpu: Extend fpu_xstate_prctl() with guest permissions Thomas Gleixner
2021-12-14 5:13 ` Tian, Kevin
2021-12-14 10:37 ` Paolo Bonzini
2021-12-14 2:50 ` [patch 2/6] x86/fpu: Prepare guest FPU for dynamically enabled FPU features Thomas Gleixner
2021-12-14 2:50 ` [patch 3/6] x86/fpu: Make XFD initialization in __fpstate_reset() a function argument Thomas Gleixner
2021-12-14 2:50 ` [patch 4/6] x86/fpu: Add guest support to xfd_enable_feature() Thomas Gleixner
2021-12-14 6:05 ` Tian, Kevin
2021-12-14 10:21 ` Paolo Bonzini
2021-12-14 13:15 ` Thomas Gleixner
2021-12-15 5:46 ` Tian, Kevin
2021-12-15 9:53 ` Thomas Gleixner
2021-12-15 10:02 ` Tian, Kevin
2021-12-14 2:50 ` [patch 5/6] x86/fpu: Provide fpu_update_guest_xcr0/xfd() Thomas Gleixner
2021-12-14 6:25 ` Tian, Kevin
2021-12-14 15:09 ` Wang, Wei W
2021-12-14 15:40 ` Thomas Gleixner
2021-12-14 16:11 ` Wang, Wei W
2021-12-14 18:04 ` Thomas Gleixner
2021-12-14 19:07 ` Juan Quintela
2021-12-14 20:28 ` Thomas Gleixner
2021-12-14 21:35 ` Juan Quintela
2021-12-15 2:17 ` Wang, Wei W
2021-12-15 10:09 ` Thomas Gleixner
2021-12-15 10:27 ` Paolo Bonzini
2021-12-15 10:41 ` Paolo Bonzini
2021-12-16 1:00 ` Tian, Kevin
2021-12-16 5:36 ` Tian, Kevin
2021-12-16 21:07 ` Paolo Bonzini
2021-12-16 10:21 ` Tian, Kevin
2021-12-16 10:24 ` Paolo Bonzini [this message]
2021-12-16 10:26 ` Paolo Bonzini
2021-12-16 13:00 ` Tian, Kevin
2021-12-16 1:04 ` Tian, Kevin
2021-12-16 9:34 ` Thomas Gleixner
2021-12-16 9:59 ` Tian, Kevin
2021-12-16 14:12 ` Thomas Gleixner
2021-12-17 15:33 ` Tian, Kevin
2021-12-15 6:14 ` Tian, Kevin
2021-12-14 2:50 ` [patch 6/6] x86/fpu: Provide kvm_sync_guest_vmexit_xfd_state() Thomas Gleixner
2021-12-15 6:35 ` Liu, Jing2
2021-12-15 9:49 ` Thomas Gleixner
2021-12-14 6:50 ` [patch 0/6] x86/fpu: Preparatory changes for guest AMX support Tian, Kevin
2021-12-14 6:52 ` Liu, Jing2
2021-12-14 7:54 ` Tian, Kevin
2021-12-14 10:42 ` Paolo Bonzini
2021-12-14 13:24 ` Thomas Gleixner
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