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Date: Wed, 17 Sep 2014 12:56:38 +0300
From: "Michael S. Tsirkin" <mst@redhat.com>
Message-ID: <20140917095638.GA11743@redhat.com>
References: <20140917083815.GA10450@redhat.com> <541956B8.1070203@huawei.com>
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Subject: Re: [Qemu-devel] vhost-user: VHOST_SET_MEM_TABLE,
 VHOST_SET_VRING_CALL need a reply?
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To: Linhaifeng <haifeng.lin@huawei.com>
Cc: qemu-devel@nongnu.org, n.nikolaev@virtualopensystems.com, jerry.lilijun@huawei.com

On Wed, Sep 17, 2014 at 05:39:04PM +0800, Linhaifeng wrote:
> I think maybe is not need for the backend to wait for response.
> 
> There is another way.vhost-user send "VHOST_GET_MEM_TABLE" to qemu then qemu send VHOST_SET_MEM_TABLE to update the regions of vhost-user.same as other command.
> If qemu could response the request of the vhost-user.the vhost-user could update date at anytime.

The updates are initiated by QEMU, as a result of IOMMU,
memory hotplug or some other configuration change.

> I think it's very useful for Commercialization.
> 
> On 2014/9/17 16:38, Michael S. Tsirkin wrote:
> > Reply-To: 
> > 
> > Thinking about the vhost-user protocol, VHOST_SET_MEM_TABLE
> > is used to update the memory mappings.
> > 
> > So shouldn't we want for response?
> > Otherwise e.g. guest can start using the memory
> > that vhost-user can't access.
> > 
> > Similarly, with an IOMMU vhost-user might access memory it shouldn't.
> > 
> > VHOST_SET_VRING_CALL is used for MSI-X masking.
> > Again, after vector is masted by switching the call fd,
> > backend shouldn't assert the old one.
> > 
> > Thoughts?
> > 
> >