linux-kernel - Re: [PATCH] x86/fpu: Allow PKRU to be (once again) written by ptrace.

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Message-ID: <899e4d3d-e086-71a5-38f9-17e85ce11ea4@redhat.com>
Date:   Wed, 3 Aug 2022 19:33:39 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Ingo Molnar <mingo@...nel.org>, Kyle Huey <me@...ehuey.com>
Cc:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>, Ingo Molnar <mingo@...hat.com>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org,
        Robert O'Callahan <robert@...llahan.org>,
        David Manouchehri <david.manouchehri@...eup.net>,
        kvm@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] x86/fpu: Allow PKRU to be (once again) written by ptrace.

On 8/3/22 19:25, Ingo Molnar wrote:
> Ok - allowing ptrace to set the full 32 bits of the PKRU register seems OK
> then, and is 100% equivalent to using WRPKRU, right? So there's no implicit
> masking/clearing of bits depending on how many keys are available, or other
> details where WRPKRU might differ from a pure 32-bit per thread write,
> correct?

Yes, it's the same.

Paolo