From: Andy Lutomirski <luto@kernel.org>
To: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
LKML <linux-kernel@vger.kernel.org>, X86 ML <x86@kernel.org>,
Andrew Lutomirski <luto@kernel.org>,
Paolo Bonzini <pbonzini@redhat.com>,
Radim Krcmar <rkrcmar@redhat.com>, kvm list <kvm@vger.kernel.org>,
"Jason A. Donenfeld" <Jason@zx2c4.com>,
Rik van Riel <riel@surriel.com>
Subject: Re: [PATCH 05/11] x86/fpu: set PKRU state for kernel threads
Date: Fri, 12 Oct 2018 11:02:18 -0700 [thread overview]
Message-ID: <CALCETrUdxsFA5g0M9uRFktfdi=mxK_g3kBfs-VxwDZ0xWqjFAQ@mail.gmail.com> (raw)
In-Reply-To: <39e0a55f-4920-cfde-9bef-09c51109d211@linux.intel.com>
On Fri, Oct 12, 2018 at 10:54 AM Dave Hansen
<dave.hansen@linux.intel.com> wrote:
>
> On 10/04/2018 07:05 AM, Sebastian Andrzej Siewior wrote:
> > The PKRU value is not set for kernel threads because they do not have
> > the ->initialized value set. As a result the kernel thread has a random
> > PKRU value set which it inherits from the previous task.
> > It has been suggested by Paolo Bonzini to set it for kernel threads, too
> > because it might be a fix.
> > I *think* this is not required because the kernel threads don't copy
> > data to/from userland and don't have access to any userspace mm in
> > general.
> > However there is this use_mm(). If we gain a mm by use_mm() we don't
> > have a matching PKRU value because those are per thread. It has been
> > suggested to use 0 as the PKRU value but this would bypass PKRU.
> >
> > Set the initial (default) PKRU value for kernel threads.
>
> We might want to do this for cleanliness reasons... Maybe.
>
> But this *should* have no practical effects. Kernel threads have no
> real 'mm' and no user pages. They should not have do access to user
> mappings. Protection keys *only* apply to user mappings. Thus,
> logically, they should never be affected by PKRU values.
>
> So I'm kinda missing the point of the patch.
use_mm().
next prev parent reply other threads:[~2018-10-12 18:02 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-04 14:05 [PATCH 00/11 v3] x86: load FPU registers on return to userland Sebastian Andrzej Siewior
2018-10-04 14:05 ` [PATCH 01/11] x86/entry: remove _TIF_ALLWORK_MASK Sebastian Andrzej Siewior
2018-10-11 16:27 ` Borislav Petkov
2018-10-04 14:05 ` [PATCH 02/11] x86/fpu: add (__)make_fpregs_active helpers Sebastian Andrzej Siewior
2018-10-04 14:05 ` [PATCH 03/11] x86/fpu: make __raw_xsave_addr() use feature number instead of mask Sebastian Andrzej Siewior
2018-10-11 17:30 ` Christophe de Dinechin
2018-10-18 11:19 ` Sebastian Andrzej Siewior
2018-10-12 15:52 ` Dave Hansen
2018-10-18 11:17 ` Sebastian Andrzej Siewior
2018-10-18 11:21 ` Sebastian Andrzej Siewior
2018-10-17 10:01 ` Borislav Petkov
2018-10-18 11:48 ` Sebastian Andrzej Siewior
2018-10-04 14:05 ` [PATCH 04/11] x86/fpu: eager switch PKRU state Sebastian Andrzej Siewior
2018-10-12 17:51 ` Dave Hansen
2018-10-12 18:09 ` Andy Lutomirski
2018-10-12 19:44 ` Dave Hansen
2018-10-18 16:13 ` Sebastian Andrzej Siewior
2018-10-18 17:50 ` Dave Hansen
2018-10-04 14:05 ` [PATCH 05/11] x86/fpu: set PKRU state for kernel threads Sebastian Andrzej Siewior
2018-10-12 17:54 ` Dave Hansen
2018-10-12 18:02 ` Andy Lutomirski [this message]
2018-10-18 16:26 ` Sebastian Andrzej Siewior
2018-10-18 16:48 ` Andy Lutomirski
2018-10-18 17:47 ` Dave Hansen
2018-10-18 18:25 ` Sebastian Andrzej Siewior
2018-10-18 20:46 ` Andy Lutomirski
2018-10-18 20:56 ` Dave Hansen
2018-10-18 21:24 ` Sebastian Andrzej Siewior
2018-10-18 21:58 ` Andy Lutomirski
2018-10-19 7:44 ` Paolo Bonzini
2018-10-19 16:59 ` Andy Lutomirski
2018-10-19 17:01 ` Dave Hansen
2018-10-19 17:37 ` Andy Lutomirski
2018-10-19 18:26 ` Dave Hansen
2018-10-04 14:05 ` [PATCH 06/11] x86/pkeys: make init_pkru_value static Sebastian Andrzej Siewior
2018-10-12 17:55 ` Dave Hansen
2018-10-04 14:05 ` [PATCH 07/11] x86/pkeys: Drop the preempt-disable section Sebastian Andrzej Siewior
2018-10-12 17:58 ` Dave Hansen
2018-10-12 18:07 ` Andy Lutomirski
2018-10-12 20:26 ` Sebastian Andrzej Siewior
2018-10-04 14:05 ` [PATCH 08/11] x86/fpu: Always store the registers in copy_fpstate_to_sigframe() Sebastian Andrzej Siewior
2018-10-11 17:50 ` Christophe de Dinechin
2018-10-11 21:18 ` Andy Lutomirski
2018-10-12 18:15 ` Dave Hansen
2018-11-02 14:42 ` Sebastian Andrzej Siewior
2018-10-04 14:05 ` [PATCH 09/11] x86/entry: add TIF_LOAD_FPU Sebastian Andrzej Siewior
2018-10-04 14:05 ` [PATCH 10/11] x86/fpu: prepare copy_fpstate_to_sigframe for TIF_LOAD_FPU Sebastian Andrzej Siewior
2018-10-12 19:40 ` Dave Hansen
2018-10-15 15:24 ` Borislav Petkov
2018-11-02 15:44 ` Sebastian Andrzej Siewior
2018-11-02 22:55 ` Sebastian Andrzej Siewior
2018-10-04 14:05 ` [PATCH 11/11] x86/fpu: defer FPU state load until return to userspace Sebastian Andrzej Siewior
2018-10-04 16:14 ` Andy Lutomirski
2018-10-12 20:25 ` Sebastian Andrzej Siewior
2018-10-04 16:45 ` [PATCH 00/11 v3] x86: load FPU registers on return to userland Rik van Riel
2018-10-04 16:50 ` Andy Lutomirski
2018-10-05 11:55 ` Sebastian Andrzej Siewior
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