From: Paolo Bonzini <pbonzini@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: aik@ozlabs.ru, aliguori@us.ibm.com, rusty@rustcorp.com.au,
qemu-devel@nongnu.org, agraf@suse.de
Subject: Re: [Qemu-devel] [PATCH] virtio: Make memory barriers be memory barriers
Date: Mon, 5 Sep 2011 05:42:21 -0400 (EDT) [thread overview]
Message-ID: <1604966537.1072741.1315215741887.JavaMail.root@zmail07.collab.prod.int.phx2.redhat.com> (raw)
In-Reply-To: <20110905080609.GB16038@redhat.com>
> > No, rmb and wmb need to generate code.
>
> If they do we'll have to surround each their use with
> ifndef x86 as you suggest later. Which is just messy.
[1 hour later]
I see what you mean now. You assume there are no accesses to
write-combining memory (of course) or non-temporal load/stores
(because they are accessed only with assembly), so you can
make rmb/wmb no-ops on x86. I was confused by the kernel
(and liburcu's) choice to use lfence/sfence for rmb/wmb.
Then it's indeed better to move the wmb() defines to
qemu-barrier.h, where they can be made processor-dependent.
S390, it seems, also does not need rmb/wmb.
Paolo
next prev parent reply other threads:[~2011-09-05 9:42 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-01 6:09 [Qemu-devel] [PATCH] virtio: Make memory barriers be memory barriers David Gibson
2011-09-01 6:47 ` Paolo Bonzini
2011-09-02 0:08 ` David Gibson
2011-09-02 6:49 ` Paolo Bonzini
2011-09-03 11:53 ` Blue Swirl
2011-09-01 7:37 ` Sasha Levin
2011-09-01 7:38 ` Sasha Levin
2011-09-01 7:56 ` Paolo Bonzini
2011-09-02 0:09 ` David Gibson
2011-09-01 15:30 ` Michael S. Tsirkin
2011-09-01 16:14 ` Paolo Bonzini
2011-09-01 16:34 ` Michael S. Tsirkin
2011-09-01 20:31 ` Paolo Bonzini
2011-09-02 15:45 ` Michael S. Tsirkin
2011-09-03 14:46 ` David Gibson
2011-09-04 9:16 ` Michael S. Tsirkin
2011-09-05 4:43 ` David Gibson
2011-09-05 9:19 ` Michael S. Tsirkin
2011-09-06 3:12 ` David Gibson
2011-09-06 6:55 ` Paolo Bonzini
2011-09-06 9:02 ` David Gibson
2011-09-06 9:28 ` Avi Kivity
2011-09-06 9:35 ` Michael S. Tsirkin
2011-09-06 9:38 ` Paolo Bonzini
2011-09-05 7:41 ` Paolo Bonzini
2011-09-05 8:06 ` Michael S. Tsirkin
2011-09-05 9:42 ` Paolo Bonzini [this message]
2011-09-03 16:19 ` Paolo Bonzini
2011-09-04 8:47 ` Michael S. Tsirkin
2011-09-02 0:11 ` David Gibson
2011-09-02 6:11 ` Paolo Bonzini
2011-09-02 15:57 ` Michael S. Tsirkin
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