From: Jason Wang <jasowang@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>,
Cornelia Huck <cornelia.huck@de.ibm.com>
Cc: rusty@rustcorp.com.au, virtualization@lists.linux-foundation.org,
linux-kernel@vger.kernel.org,
Wanlong Gao <gaowanlong@cn.fujitsu.com>
Subject: Re: [PATCH V3 1/2] virtio: introduce methods of sanitizing device features
Date: Tue, 18 Nov 2014 11:23:49 +0800 [thread overview]
Message-ID: <546ABBC5.7030603@redhat.com> (raw)
In-Reply-To: <20141117101139.GE20133@redhat.com>
On 11/17/2014 06:11 PM, Michael S. Tsirkin wrote:
> On Mon, Nov 17, 2014 at 10:44:30AM +0100, Cornelia Huck wrote:
>> On Mon, 17 Nov 2014 11:37:01 +0200
>> "Michael S. Tsirkin" <mst@redhat.com> wrote:
>>
>>> On Mon, Nov 17, 2014 at 05:17:17PM +0800, Jason Wang wrote:
>>>> Buggy host may advertised buggy host features (a usual case is that host
>>>> advertise a feature whose dependencies were missed). In this case, driver
>>>> should detect and disable the buggy features by itself.
>>>>
>>>> This patch introduces driver specific sanitize_features() method which is
>>>> called just before features finalizing to detect and disable buggy features
>>>> advertised by host.
>>>>
>>>> Virtio-net will be the first user.
>>>>
>>>> Cc: Rusty Russell <rusty@rustcorp.com.au>
>>>> Cc: Michael S. Tsirkin <mst@redhat.com>
>>>> Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
>>>> Cc: Wanlong Gao <gaowanlong@cn.fujitsu.com>
>>>> Signed-off-by: Jason Wang <jasowang@redhat.com>
>>> Hmm this conflicts with virtio 1.0 work: we drop
>>> features as bitmap there.
>> But that's an implementation detail, no? We'll still need a way for the
>> driver to sanitize features, and I think this interface works just fine.
> Now that you mention it, I don't think we do.
>
> The spec is quite explicit that devices must not expose invalid
> combinations of features.
>
> Admittedly, BUG_ON isn't very friendly to hypervisors.
>
> But e.g. failing probe seems better than trying to work around
> hypervisor bugs - otherwise we'll be stuck maintaining compatibility
> with hypervisors forever.
>
I'm ok with failing the probe.
But it won't cost big effort to workaround only features dependencies
issue. I don't see how this block any further features implementation.
Looking at virtio-net, it also depends on network core to fix NETIF_F_*
dependencies.
There seems no way to get rid of maintaining compatibility, e.g the
workarounds for the buggy hypervisor without VIRTIO_F_ANY_LAYOUT support.
next prev parent reply other threads:[~2014-11-18 3:24 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-17 9:17 [PATCH V3 1/2] virtio: introduce methods of sanitizing device features Jason Wang
2014-11-17 9:17 ` [PATCH V3 2/2] virtio-net: sanitize buggy features advertised by host Jason Wang
2014-11-17 10:08 ` Michael S. Tsirkin
2014-11-18 3:03 ` Jason Wang
2014-11-18 11:02 ` Michael S. Tsirkin
2014-11-17 9:37 ` [PATCH V3 1/2] virtio: introduce methods of sanitizing device features Michael S. Tsirkin
2014-11-17 9:44 ` Cornelia Huck
2014-11-17 10:11 ` Michael S. Tsirkin
2014-11-17 10:20 ` Cornelia Huck
2014-11-17 10:28 ` Michael S. Tsirkin
2014-11-17 11:20 ` Cornelia Huck
2014-11-18 3:23 ` Jason Wang [this message]
2014-11-18 11:04 ` Michael S. Tsirkin
2014-11-19 3:00 ` Jason Wang
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