Re: [RFC PATCH v4 11/20] vhost: Route host->guest notification through shadow virtqueue

From: Jason Wang <jasowang@redhat.com>
To: Eugenio Perez Martin <eperezma@redhat.com>
Cc: Parav Pandit <parav@mellanox.com>,
	Markus Armbruster <armbru@redhat.com>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	qemu-level <qemu-devel@nongnu.org>,
	virtualization <virtualization@lists.linux-foundation.org>,
	Harpreet Singh Anand <hanand@xilinx.com>,
	Xiao W Wang <xiao.w.wang@intel.com>,
	Stefan Hajnoczi <stefanha@redhat.com>,
	Eli Cohen <eli@mellanox.com>, Eric Blake <eblake@redhat.com>,
	Michael Lilja <ml@napatech.com>
Subject: Re: [RFC PATCH v4 11/20] vhost: Route host->guest notification through shadow virtqueue
Date: Fri, 15 Oct 2021 12:24:37 +0800	[thread overview]
Message-ID: <8a68a144-ee7c-6e12-ebf0-e72aaa7d1e3c@redhat.com> (raw)
In-Reply-To: <CAJaqyWcQ314RN7-U1bYqCMXb+-nyhSi3ddqWv90ofFucMbveUw@mail.gmail.com>

在 2021/10/14 下午11:58, Eugenio Perez Martin 写道:
> On Wed, Oct 13, 2021 at 5:49 AM Jason Wang <jasowang@redhat.com> wrote:
>>
>> 在 2021/10/1 下午3:05, Eugenio Pérez 写道:
>>> This will make qemu aware of the device used buffers, allowing it to
>>> write the guest memory with its contents if needed.
>>>
>>> Since the use of vhost_virtqueue_start can unmasks and discard call
>>> events, vhost_virtqueue_start should be modified in one of these ways:
>>> * Split in two: One of them uses all logic to start a queue with no
>>>     side effects for the guest, and another one tha actually assumes that
>>>     the guest has just started the device. Vdpa should use just the
>>>     former.
>>> * Actually store and check if the guest notifier is masked, and do it
>>>     conditionally.
>>> * Left as it is, and duplicate all the logic in vhost-vdpa.
>>
>> Btw, the log looks not clear. I guess this patch goes for method 3. If
>> yes, we need explain it and why.
>>
>> Thanks
>>
> Sorry about being unclear. This commit log (and code) just exposes the
> problem and the solutions I came up with but does nothing to solve it.
> I'm actually going for method 3 for the next series but I'm open to
> doing it differently.

That's fine, but need to doc that method 3 is something that is done in 
the patch.

Thanks

>
>>> Signed-off-by: Eugenio Pérez<eperezma@redhat.com>

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