All of lore.kernel.org
 help / color / mirror / Atom feed
From: Dave Hansen <dave.hansen@intel.com>
To: Andy Lutomirski <luto@kernel.org>, Borislav Petkov <bp@alien8.de>
Cc: X86 ML <x86@kernel.org>,
	jpa@kernelbug.mail.kapsi.fi, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/2] x86/fpu: Reset MXCSR to default in kernel_fpu_begin()
Date: Mon, 22 Jun 2020 11:38:04 -0700	[thread overview]
Message-ID: <ef327682-7e9f-5652-1664-3e201ac38f60@intel.com> (raw)
In-Reply-To: <CALCETrU0C5yVwfAOj+v1RqNBZY+phXrdvCBZMKdOXOExBgMbVg@mail.gmail.com>

On 6/22/20 11:33 AM, Andy Lutomirski wrote:
> Suppose you do:
> 
> double x = 1.0;
> 
> kernel_fpu_begin();
> 
> x += 2.0;
> 
> We want to make sure that GCC puts things in the right order.  I
> suppose that even a memory clobber is insufficient here, though.

Even with CONFIG_PREEMPT disabled, we still have:

	#define preempt_disable()                       barrier()

I don't see us supporting preemptible kernel_fpu regions any time soon,
so shouldn't this be sufficient now and for a long time?

  parent reply	other threads:[~2020-06-22 18:38 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-19 17:41 [PATCH 0/2] x86/FPU: FPU sanitization for in-kernel use Borislav Petkov
2020-06-19 17:41 ` [PATCH 1/2] x86/fpu: Reset MXCSR to default in kernel_fpu_begin() Borislav Petkov
2020-06-19 18:01   ` Andy Lutomirski
2020-06-22 17:09     ` Borislav Petkov
2020-06-22 18:33       ` Andy Lutomirski
2020-06-22 18:36         ` Petteri Aimonen
2020-06-22 18:38         ` Dave Hansen [this message]
2020-06-22 18:40           ` Andy Lutomirski
2020-06-22 18:59             ` Borislav Petkov
2020-06-19 17:41 ` [PATCH 2/2] selftests/fpu: Add an FPU selftest Borislav Petkov
2020-06-19 18:00   ` Andy Lutomirski
2020-06-22 17:12     ` Borislav Petkov
2020-06-22 18:26       ` Andy Lutomirski
2020-06-22 19:01         ` Borislav Petkov
     [not found]           ` <B4D00859-000A-4F8C-8CFB-45B9BBCCA16D@amacapital.net>
2020-06-23 10:28             ` Borislav Petkov
2020-06-23 18:22               ` Andy Lutomirski
2020-06-23 18:47                 ` Borislav Petkov
2020-06-23 19:07                   ` Nick Desaulniers
2020-06-23 19:13                     ` Borislav Petkov
2020-06-23 20:58                       ` Nick Desaulniers
2020-06-23 21:32                         ` Borislav Petkov
2020-06-20 19:55   ` kernel test robot
2020-06-20 19:55     ` kernel test robot
2020-06-22 17:04     ` Borislav Petkov
2020-06-22 17:04       ` Borislav Petkov
2020-06-22 18:15       ` Nick Desaulniers
2020-06-22 18:15         ` Nick Desaulniers

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=ef327682-7e9f-5652-1664-3e201ac38f60@intel.com \
    --to=dave.hansen@intel.com \
    --cc=bp@alien8.de \
    --cc=jpa@kernelbug.mail.kapsi.fi \
    --cc=linux-kernel@vger.kernel.org \
    --cc=luto@kernel.org \
    --cc=x86@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.