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From: Vincent Whitchurch <firstname.lastname@example.org>
To: "Michael S. Tsirkin" <email@example.com>
Cc: Jason Wang <firstname.lastname@example.org>, kernel <email@example.com>,
Subject: Re: [PATCH] vhost: add support for mandatory barriers
Date: Tue, 24 Aug 2021 09:23:06 +0200 [thread overview]
Message-ID: <20210824072306.GA29073@axis.com> (raw)
On Mon, Aug 23, 2021 at 11:19:56PM +0200, Michael S. Tsirkin wrote:
> On Mon, Aug 23, 2021 at 10:14:37AM +0200, Vincent Whitchurch wrote:
> > vhost always uses SMP-conditional barriers, but these may not be
> > sufficient when vhost is used to communicate between heterogeneous
> > processors in an AMP configuration, especially since they're NOPs on
> > !SMP builds.
> > To solve this, use the virtio_*() barrier functions and ask them for
> > non-weak barriers if requested by userspace.
> > Signed-off-by: Vincent Whitchurch <firstname.lastname@example.org>
> I am inclined to say let's (ab)use VIRTIO_F_ORDER_PLATFORM for this.
> Jason what do you think?
OK, thanks, I'll look into that.
> Also is the use of DMA variants really the intended thing here? Could
> you point me at some examples please?
I'm using this on an ARM-based SoC. The main processor is a Cortex-A53
(arm64) and this processor runs the virtio drivers. The SoC also has
another processor which is a Cortex-A5 (arm32) and this processor runs
the virtio device end using vhost. There is no coherency between these
two processors and to each other they look like any other DMA-capable
prev parent reply other threads:[~2021-08-24 7:23 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-23 8:14 Vincent Whitchurch
2021-08-23 21:19 ` Michael S. Tsirkin
2021-08-24 2:56 ` Jason Wang
2021-08-24 7:23 ` Vincent Whitchurch [this message]
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