Re: [Qemu-devel] vhost-user: VHOST_SET_MEM_TABLE, VHOST_SET_VRING_CALL need a reply?

[Michael S. Tsirkin]

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?
> > 
> >