Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Message-ID: <11aa7d0f4ba36eff8b61a5dc1bd35ee5195fd576.camel@surriel.com>
Subject: Re: [RFC PATCH 04/10 v2 ] x86/fpu: eager switch PKRU state
From:   Rik van Riel <riel@surriel.com>
To:     Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        Paolo Bonzini <pbonzini@redhat.com>
Cc:     linux-kernel@vger.kernel.org, x86@kernel.org,
        Andy Lutomirski <luto@kernel.org>,
        Radim =?UTF-8?Q?Kr=C4=8Dm=C3=A1=C5=99?= <rkrcmar@redhat.com>,
        kvm@vger.kernel.org, "Jason A. Donenfeld" <Jason@zx2c4.com>
Date:   Tue, 18 Sep 2018 13:29:01 -0400
In-Reply-To: <20180918160419.2zeru6xnufxixcax@linutronix.de>
References: <20180912133353.20595-1-bigeasy@linutronix.de>
         <20180912133353.20595-5-bigeasy@linutronix.de>
         <8e5b64e4-b3e6-f884-beb6-b7b69ab2d8c1@redhat.com>
         <20180914203501.qibhpmueosvkr74w@linutronix.de>
         <a239e97a-d1a1-388e-5db9-10758c33d702@redhat.com>
         <20180918142701.atfb4ul45k7tl6ew@linutronix.de>
         <7e9a13f3-93f5-fe4a-20d2-f4f9407bd43b@redhat.com>
         <83e271e1298d603c1105dd0dbea32d67da9cf1fa.camel@surriel.com>
         <36e8493f-f994-e885-8fe6-2f0d4a9904a1@redhat.com>
         <20180918160419.2zeru6xnufxixcax@linutronix.de>
Content-Type: multipart/signed; micalg="pgp-sha256";
        protocol="application/pgp-signature"; boundary="=-qeo8C7RCdou6hmINJRZf"
Mime-Version: 1.0
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


--=-qeo8C7RCdou6hmINJRZf
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

On Tue, 2018-09-18 at 18:04 +0200, Sebastian Andrzej Siewior wrote:
> On 2018-09-18 17:29:52 [+0200], Paolo Bonzini wrote:
> > > I don't think it matters what the PKRU state is
> > > for kernel threads, since kernel PTEs should not
> > > be using protection keys anyway.
> >=20
> > What about copy_from/to_user?
>=20
> This doesn't work for a kernel thread, does it? I mean they share the
> init's MM and never do copy_{from|to}_user.

Indeed, copy_from/to_user only works if current->mm
points at an mm_struct with userspace memory.

--=20
All Rights Reversed.

--=-qeo8C7RCdou6hmINJRZf
Content-Type: application/pgp-signature; name="signature.asc"
Content-Description: This is a digitally signed message part
Content-Transfer-Encoding: 7bit

-----BEGIN PGP SIGNATURE-----

iQEzBAABCAAdFiEEKR73pCCtJ5Xj3yADznnekoTE3oMFAluhNd0ACgkQznnekoTE
3oN7+Af9GJYyy55zxm7fhdOa+X8DIovy7Le9zNpPgqRaoQLhctM69+uvP1wF7oQY
V3wf3MrXD9eXq+DJHKqKFpfGcTAlIgl8YclJaEVE1vQjoKeYvfRmaXvMd+7Wguhv
+3PeKQ9H5KD8w266Z/tUXJOh/Nxbtkd3Qvvx86bv6uiSkd4rqhYihi7x9n6biU2R
UgxsbfPh/rmPN0RpNtAbPaWdq6XQ3SU/Z364+bMNFpW7kBVhMMw53D/ldpwusfo9
q9uvmSrA+DUtZloPpGaEMopMfpnnyby3EZ5Q+scfwC6YO0x9BoxKk0fOS2ImE++z
6tiOxmI1os93JUV7NLCOOL7Bpd7WGQ==
=HdUP
-----END PGP SIGNATURE-----

--=-qeo8C7RCdou6hmINJRZf--