From: Rusty Russell <rusty@rustcorp.com.au>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: virtualization@lists.linux-foundation.org
Subject: Re: [PATCHv2] virtio: use smp_XX barriers on SMP
Date: Thu, 28 Jan 2010 10:01:09 +1030 [thread overview]
Message-ID: <201001281001.09999.rusty@rustcorp.com.au> (raw)
In-Reply-To: <20100127224222.GA31545@redhat.com>
On Thu, 28 Jan 2010 09:12:23 am Michael S. Tsirkin wrote:
> virtio is communicating with a virtual "device" that actually runs on
> another host processor. Thus SMP barriers can be used to control
> memory access ordering.
>
> Where possible, we should use SMP barriers which are more lightweight than
> mandatory barriers, because mandatory barriers also control MMIO effects on
> accesses through relaxed memory I/O windows (which virtio does not use)
> (compare specifically smp_rmb and rmb on x86_64).
Xen had a similar issue, in that UP guests running on SMP hosts need to issue
SMP barriers. Is this not also a requirement for virtio?
But I'm not sure what came out of the discussion: Jeremy?
Cheers,
Rusty.
next prev parent reply other threads:[~2010-01-27 23:31 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-01-27 22:42 [PATCHv2] virtio: use smp_XX barriers on SMP Michael S. Tsirkin
2010-01-27 23:31 ` Rusty Russell [this message]
2010-01-28 13:37 ` Michael S. Tsirkin
2010-01-28 21:14 ` Rusty Russell
2010-01-29 11:27 ` Michael S. Tsirkin
2010-01-30 4:52 ` Rusty Russell
2010-01-29 13:48 ` Michael S. Tsirkin
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