From: Paolo Bonzini <pbonzini@redhat.com>
To: Avi Kivity <avi@redhat.com>
Cc: aliguori@us.ibm.com, "Michael S. Tsirkin" <mst@redhat.com>,
aik@ozlabs.ru, rusty@rustcorp.com.au, agraf@suse.de,
qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH] virtio: Make memory barriers be memory barriers
Date: Tue, 06 Sep 2011 11:38:59 +0200 [thread overview]
Message-ID: <4E65EA33.30807@redhat.com> (raw)
In-Reply-To: <4E65E7C8.4080602@redhat.com>
On 09/06/2011 11:28 AM, Avi Kivity wrote:
>>
>> Actually Michael is right. The implementation is correct on x86,
>> though wrong anywhere else (perhaps s390?). On those architectures
>> you do not need rmb() and wmb().
>
> Are we sure? Nothing prevents the guest from using weakly-ordered
> writes, is there? For example, using MOVNTDQ.
>
> Although in that case the guest is probably required to issue an SFENCE.
Yes, that's the guest problem. You cannot do an SFENCE on the guest's
behalf anyway.
Paolo
next prev parent reply other threads:[~2011-09-06 9:39 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 [this message]
2011-09-05 7:41 ` Paolo Bonzini
2011-09-05 8:06 ` Michael S. Tsirkin
2011-09-05 9:42 ` Paolo Bonzini
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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