From: Sean Christopherson <seanjc@google.com>
To: Kyle Huey <me@kylehuey.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Borislav Petkov <bp@alien8.de>, Ingo Molnar <mingo@redhat.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
linux-kselftest@vger.kernel.org,
Robert O'Callahan <robert@ocallahan.org>,
David Manouchehri <david.manouchehri@riseup.net>,
Borislav Petkov <bp@suse.de>,
stable@vger.kernel.org
Subject: Re: [PATCH v6 1/2] x86/fpu: Allow PKRU to be (once again) written by ptrace.
Date: Thu, 1 Sep 2022 15:29:46 +0000 [thread overview]
Message-ID: <YxDP6jie4cwzZIHp@google.com> (raw)
In-Reply-To: <20220829194905.81713-1-khuey@kylehuey.com>
On Mon, Aug 29, 2022, Kyle Huey wrote:
> @@ -1246,6 +1246,21 @@ static int copy_uabi_to_xstate(struct fpstate *fpstate, const void *kbuf,
> }
> }
>
> + /*
> + * Update the user protection key storage. Allow KVM to
> + * pass in a NULL pkru pointer if the mask bit is unset
> + * for its legacy ABI behavior.
> + */
> + if (pkru)
> + *pkru = 0;
> +
> + if (hdr.xfeatures & XFEATURE_MASK_PKRU) {
> + struct pkru_state *xpkru;
> +
> + xpkru = __raw_xsave_addr(xsave, XFEATURE_PKRU);
> + *pkru = xpkru->pkru;
> + }
What about writing this as:
if (hdr.xfeatures & XFEATURE_MASK_PKRU) {
...
*pkru = xpkru->pkru;
} else if (pkru) {
*pkru = 0;
}
to make it slightly more obvious that @pkru must be non-NULL if the feature flag
is enabled?
Or we could be paranoid, though I'm not sure this is worthwhile.
if ((hdr.xfeatures & XFEATURE_MASK_PKRU) &&
!WARN_ON_ONCE(!pkru)) {
...
*pkru = xpkru->pkru;
} else if (pkru) {
*pkru = 0;
}
Otherwise, looks good from a KVM perspective. Thanks!
next prev parent reply other threads:[~2022-09-01 15:30 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-29 19:49 [PATCH v6 1/2] x86/fpu: Allow PKRU to be (once again) written by ptrace Kyle Huey
2022-09-01 15:29 ` Sean Christopherson [this message]
2022-09-02 14:55 ` Kyle Huey
2022-09-14 4:08 ` Kyle Huey
-- strict thread matches above, loose matches on Subject: below --
2022-10-03 20:42 Kyle Huey
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