Re: [PATCH] virtio-spec: clarify ro/rw bits and updating rule of virtio-net status field
From: "Michael S. Tsirkin" <mst@redhat.com>
Date: 2012-03-21 06:37:41
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- 2012-03-20 · Re: [PATCH] virtio-spec: clarify ro/rw bits and updating rule of virtio-net status field · Rusty Russell <hidden>
- 2012-03-20 · [PATCH] virtio-spec: clarify ro/rw bits and updating rule of virtio-net status field · Jason Wang <jasowang@redhat.com>
On Wed, Mar 21, 2012 at 10:10:52AM +1030, Rusty Russell wrote:
On Wed, 21 Mar 2012 00:48:05 +0200, "Michael S. Tsirkin" [off-list ref] wrote:quoted
On Tue, Mar 20, 2012 at 09:35:18PM +1030, Rusty Russell wrote:quoted
On Tue, 20 Mar 2012 14:20:21 +0800, Jason Wang [off-list ref] wrote:quoted
This patch clarifies VIRTIO_NET_S_LINK_UP as a read-only bit and VIRTIO_NET_S_ANNOUNCE as a read-writable bit. Also introduce the write 1 to clear semantics for all read-writable bits of config status field. This could help to reduce the config status field updating race between host and guest and also simplify the implementation. Signed-off-by: Jason Wang <jasowang@redhat.com>This approach assumes an active config field, which neither lguest nor S/390 have. Thanks, Rusty.What does 'active' mean in this context?It means you are assuming that writes to the config field trap to the host. Rusty.
Ah. Right, we need to trap for host to clear the bit. OK, so let's make the bit RO, and add VIRTIO_NET_CTRL_ANNOUNCED to acknowledge that we've seen VIRTIO_NET_S_ANNOUNCE using the control VQ? If there's no ctrl VQ, we won't acknowledge the feature bit ...
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