From: Cyrill Gorcunov <gorcunov@gmail.com>
To: Ian Campbell <ian.campbell@citrix.com>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
Thomas Gleixner <tglx@linutronix.de>,
"H. Peter Anvin" <hpa@zytor.com>, Brian Gerst <brgerst@gmail.com>,
Jan Beulich <JBeulich@novell.com>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Frederic Weisbecker <fweisbec@gmail.com>,
x86@kernel.org
Subject: Re: [PATCH 1/3] x86: drop unnecessary kernel_eflags variable from 64 bit.
Date: Tue, 5 Jul 2011 17:28:25 +0400 [thread overview]
Message-ID: <20110705132825.GA3900@sun> (raw)
In-Reply-To: <1309870814-14181-1-git-send-email-ian.campbell@citrix.com>
On Tue, Jul 05, 2011 at 02:00:12PM +0100, Ian Campbell wrote:
> For no reason that I can determine 64 bit x86 saves the current eflags
> in cpu_init purely for use in ret_from_fork. The equivalent 32 bit
> code simply hard codes 0x0202 as the new EFLAGS which seems safer than
> relying on a potentially arbitrary EFLAGS saved during cpu_init.
>
> Original i386 changeset
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=47a5c6fa0e204a2b63309c648bb2fde36836c826
> Original x86_64 changset
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=658fdbef66e5e9be79b457edc2cbbb3add840aa9
>
> The only comment in the later indicates that it is following the
> former, but not why it differs in this way.
>
> This change makes 64 bit use the same mechanism to setup the initial
> EFLAGS on fork. Note that 64 bit resets EFLAGS before calling
> schedule_tail() as opposed to 32 bit which calls schedule_tail()
> first. Therefore the correct value for EFLAGS has opposite IF
> bit. This will be fixed in a subsequent patch.
>
> Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
> Cc: x86@kernel.org
The whole series looks good to me, thanks Ian! I hope I don't
miss anything, so lets wait for more feedback ;)
Cyrill
next prev parent reply other threads:[~2011-07-05 13:28 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-07-05 10:47 [Q x86-64] on kernel_eflags Cyrill Gorcunov
2011-07-05 11:00 ` Ian Campbell
2011-07-05 11:15 ` Cyrill Gorcunov
2011-07-05 13:00 ` [PATCH 1/3] x86: drop unnecessary kernel_eflags variable from 64 bit Ian Campbell
2011-07-05 13:28 ` Cyrill Gorcunov [this message]
2011-07-06 9:25 ` Ian Campbell
2011-07-06 9:46 ` Cyrill Gorcunov
2011-07-06 9:57 ` Ian Campbell
2011-07-06 10:12 ` Cyrill Gorcunov
2011-07-06 9:39 ` Pekka Enberg
2011-07-06 23:17 ` Andi Kleen
2011-07-07 0:00 ` H. Peter Anvin
2011-07-05 13:00 ` [PATCH 2/3] x86: make 64 bit ret_from_fork a little more similar to 32 bit Ian Campbell
2011-07-06 9:41 ` Pekka Enberg
2011-07-05 13:00 ` [PATCH 3/3] x86: ret_from_fork: use symbolic contants for bits in EFLAGS Ian Campbell
2011-07-06 9:36 ` Pekka Enberg
2011-07-05 17:47 ` [Q x86-64] on kernel_eflags H. Peter Anvin
2011-07-05 17:56 ` Cyrill Gorcunov
2011-07-06 9:25 ` Ian Campbell
-- strict thread matches above, loose matches on Subject: below --
2011-07-25 9:58 [PATCH 0/3] minor cleanups to EFLAGS initialisation in ret_from_fork Ian Campbell
2011-07-25 10:03 ` [PATCH 1/3] x86: drop unnecessary kernel_eflags variable from 64 bit Ian Campbell
2010-02-09 15:56 [PATCH 0/3] x86: slightly unify ret_from_fork Ian Campbell
2010-02-09 15:56 ` [PATCH 1/3] x86: drop unnecessary kernel_eflags variable from 64 bit Ian Campbell
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