From: "Michael S. Tsirkin" <mst@redhat.com>
To: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
"H. Peter Anvin" <hpa@zytor.com>,
Andy Lutomirski <luto@amacapital.net>,
Andy Lutomirski <luto@kernel.org>,
Davidlohr Bueso <dave@stgolabs.net>,
Davidlohr Bueso <dbueso@suse.de>,
Peter Zijlstra <peterz@infradead.org>,
the arch/x86 maintainers <x86@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
virtualization <virtualization@lists.linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH 3/4] x86,asm: Re-work smp_store_mb()
Date: Wed, 13 Jan 2016 19:00:13 +0200 [thread overview]
Message-ID: <20160113185644-mutt-send-email-mst@redhat.com> (raw)
In-Reply-To: <20160113165319.GJ12897@pd.tnic>
On Wed, Jan 13, 2016 at 05:53:20PM +0100, Borislav Petkov wrote:
> On Wed, Jan 13, 2016 at 06:42:48PM +0200, Michael S. Tsirkin wrote:
> > Oh, I think this means we need a "cc" clobber.
>
> Btw, does your microbenchmark do it too?
Yes - I fixed it now, but it did not affect the result.
We'd need some code where gcc carries flags around though.
> Because, the "cc" clobber should cause additional handling of flags,
> depending on the context. It won't matter if the context doesn't need
> rFLAGS handling in the benchmark but if we start using LOCK; ADD in the
> kernel, I can imagine some places where mb() is used and rFLAGS are
> live, causing gcc to either reorder code or stash them away...
It will reorder code but not necessarily for the worse :)
Best I can do, I will add cc clobber to kernel and see whether
binary size grows.
> --
> Regards/Gruss,
> Boris.
>
> ECO tip #101: Trim your mails when you reply.
next prev parent reply other threads:[~2016-01-13 17:00 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-27 19:53 [PATCH -tip 0/4] A few updates around smp_store_mb() Davidlohr Bueso
2015-10-27 19:53 ` [PATCH 1/4] arch,cmpxchg: Remove tas() definitions Davidlohr Bueso
2015-10-27 23:27 ` David Howells
2015-12-04 12:01 ` [tip:locking/core] locking/cmpxchg, arch: " tip-bot for Davidlohr Bueso
2015-10-27 19:53 ` [PATCH 2/4] arch,barrier: Use smp barriers in smp_store_release() Davidlohr Bueso
2015-10-27 20:03 ` Davidlohr Bueso
2015-12-04 12:01 ` [tip:locking/core] lcoking/barriers, arch: " tip-bot for Davidlohr Bueso
2015-10-27 19:53 ` [PATCH 3/4] x86,asm: Re-work smp_store_mb() Davidlohr Bueso
2015-10-27 21:33 ` Linus Torvalds
2015-10-27 22:01 ` Davidlohr Bueso
2015-10-27 22:37 ` Peter Zijlstra
2015-10-28 19:49 ` Davidlohr Bueso
2015-11-02 20:15 ` Davidlohr Bueso
2015-11-03 0:06 ` Linus Torvalds
2015-11-03 1:36 ` Davidlohr Bueso
2016-01-12 13:57 ` Michael S. Tsirkin
2016-01-12 13:57 ` Michael S. Tsirkin
2016-01-12 17:20 ` Linus Torvalds
2016-01-12 17:20 ` Linus Torvalds
2016-01-12 17:45 ` Michael S. Tsirkin
2016-01-12 17:45 ` Michael S. Tsirkin
2016-01-12 18:04 ` Linus Torvalds
2016-01-12 18:04 ` Linus Torvalds
2016-01-12 20:30 ` Andy Lutomirski
2016-01-12 20:54 ` Linus Torvalds
2016-01-12 20:54 ` Linus Torvalds
2016-01-12 20:59 ` Andy Lutomirski
2016-01-12 20:59 ` Andy Lutomirski
2016-01-12 21:37 ` Linus Torvalds
2016-01-12 21:37 ` Linus Torvalds
2016-01-12 22:14 ` Michael S. Tsirkin
2016-01-12 22:14 ` Michael S. Tsirkin
2016-01-13 16:20 ` Michael S. Tsirkin
2016-01-13 16:20 ` Michael S. Tsirkin
2016-01-12 22:21 ` Michael S. Tsirkin
2016-01-12 22:21 ` Michael S. Tsirkin
2016-01-12 22:55 ` H. Peter Anvin
2016-01-12 22:55 ` H. Peter Anvin
2016-01-12 23:24 ` Linus Torvalds
2016-01-12 23:24 ` Linus Torvalds
2016-01-13 16:17 ` Borislav Petkov
2016-01-13 16:17 ` Borislav Petkov
2016-01-13 16:25 ` Michael S. Tsirkin
2016-01-13 16:25 ` Michael S. Tsirkin
2016-01-13 16:33 ` Borislav Petkov
2016-01-13 16:33 ` Borislav Petkov
2016-01-13 16:42 ` Michael S. Tsirkin
2016-01-13 16:42 ` Michael S. Tsirkin
2016-01-13 16:53 ` Borislav Petkov
2016-01-13 16:53 ` Borislav Petkov
2016-01-13 17:00 ` Michael S. Tsirkin
2016-01-13 17:00 ` Michael S. Tsirkin [this message]
2016-01-13 18:38 ` Linus Torvalds
2016-01-13 18:38 ` Linus Torvalds
2015-10-27 19:53 ` [PATCH 4/4] doc,smp: Remove ambiguous statement in smp_store_mb() Davidlohr Bueso
2015-12-04 12:01 ` [tip:locking/core] locking/barriers, arch: Remove ambiguous statement in the smp_store_mb() documentation tip-bot for Davidlohr Bueso
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