From: "H. Peter Anvin" <hpa@zytor.com>
To: Michal Hocko <mhocko@suse.cz>, Borislav Petkov <bp@alien8.de>
Cc: Ingo Molnar <mingo@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Jiri Kosina <jkosina@suse.cz>, Michael Matz <matz@suse.de>,
lkml <linux-kernel@vger.kernel.org>,
Ralf Baechle <ralf@linux-mips.org>
Subject: Re: [RFC] x86: Disable traditional FPU instructions too
Date: Tue, 28 Jan 2014 02:25:09 -0800 [thread overview]
Message-ID: <30d5350d-2f0d-4103-a28d-cb9b796fd8ce@email.android.com> (raw)
In-Reply-To: <20140128093701.GC2221@dhcp22.suse.cz>
If that is intentional it needs a big huge freaking comment recording why it is not a bug. I would expect that to generate a FP multiply.
On January 28, 2014 1:37:01 AM PST, Michal Hocko <mhocko@suse.cz> wrote:
>[CCing Ralf for MIPS.]
>
>On Mon 27-01-14 17:45:44, Borislav Petkov wrote:
>> On Mon, Jan 27, 2014 at 08:41:09AM -0800, H. Peter Anvin wrote:
>> > I don't think it'd hurt... although I think the above pretty much
>> > requires that the code contain actual floating-point types to ever
>be
>> > generated.
>>
>> Yes, that is supposed to catch usage of the 'E' floating constant,
>for
>> example, in definitions. It is a build-time assertion, if you want.
>:)
>
>And git grep says that mips abuses this notation:
>arch/mips/include/asm/kvm_host.h:#define MS_TO_NS(x) (x * 1E6L)
>
>I do not have cross-compiler set up to check whether this is a real
>issue because include/media/rc-core.h defines the same macro correctly
>so the real code might end up using the right variant.
--
Sent from my mobile phone. Please pardon brevity and lack of formatting.
next prev parent reply other threads:[~2014-01-28 10:26 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-27 16:37 [RFC] x86: Disable traditional FPU instructions too Borislav Petkov
2014-01-27 16:41 ` H. Peter Anvin
2014-01-27 16:43 ` Jiri Kosina
2014-01-27 17:01 ` Andi Kleen
2014-01-27 17:16 ` H. Peter Anvin
2014-01-27 17:24 ` Borislav Petkov
2014-01-27 16:45 ` Borislav Petkov
2014-01-28 9:37 ` Michal Hocko
2014-01-28 10:25 ` H. Peter Anvin [this message]
2014-01-28 10:33 ` Michal Hocko
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