Sender: Paolo Bonzini <paolo.bonzini@gmail.com>
Message-ID: <10514d6f-672b-5f1e-3af0-6eb641845c32@redhat.com>
Date:   Tue, 14 Dec 2021 11:37:39 +0100
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Subject: Re: [patch 1/6] x86/fpu: Extend fpu_xstate_prctl() with guest
 permissions
Content-Language: en-US
To:     "Tian, Kevin" <kevin.tian@intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        LKML <linux-kernel@vger.kernel.org>
Cc:     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>
References: <20211214022825.563892248@linutronix.de>
 <20211214024947.818549574@linutronix.de>
 <BN9PR11MB5276B6158AC37CA38201D4308C759@BN9PR11MB5276.namprd11.prod.outlook.com>
From:   Paolo Bonzini <pbonzini@redhat.com>
In-Reply-To: <BN9PR11MB5276B6158AC37CA38201D4308C759@BN9PR11MB5276.namprd11.prod.outlook.com>
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On 12/14/21 06:13, Tian, Kevin wrote:
>>    2) Permissions are frozen when the first vCPU is created to ensure
>>       consistency. Any attempt to expand permissions via the prctl() after
>>       that point is rejected.
>
> A curiosity question. Do we allow the user to reduce permissions?

No, there's no prctl for that.

Paolo