Re: [Qemu-devel] [PATCH 6/6] spec/vhost-user spec: Add IOMMU support

[Michael S. Tsirkin]

On Mon, May 15, 2017 at 01:45:28PM +0800, Jason Wang wrote:
> 
> 
> On 2017年05月13日 08:02, Michael S. Tsirkin wrote:
> > On Fri, May 12, 2017 at 04:21:58PM +0200, Maxime Coquelin wrote:
> > > 
> > > On 05/11/2017 08:25 PM, Michael S. Tsirkin wrote:
> > > > On Thu, May 11, 2017 at 02:32:46PM +0200, Maxime Coquelin wrote:
> > > > > This patch specifies and implements the master/slave communication
> > > > > to support device IOTLB in slave.
> > > > > 
> > > > > The vhost_iotlb_msg structure introduced for kernel backends is
> > > > > re-used, making the design close between the two backends.
> > > > > 
> > > > > An exception is the use of the secondary channel to enable the
> > > > > slave to send IOTLB miss requests to the master.
> > > > > 
> > > > > Signed-off-by: Maxime Coquelin <address@hidden>
> > > > > ---
> > > > >    docs/specs/vhost-user.txt | 75 
> > > > > +++++++++++++++++++++++++++++++++++++++++++++++
> > > > >    hw/virtio/vhost-user.c    | 31 ++++++++++++++++++++
> > > > >    2 files changed, 106 insertions(+)
> > > > > 
> > > > > diff --git a/docs/specs/vhost-user.txt b/docs/specs/vhost-user.txt
> > > > > index 5fa7016..4a1f0c3 100644
> > > > > --- a/docs/specs/vhost-user.txt
> > > > > +++ b/docs/specs/vhost-user.txt
> > > > > @@ -97,6 +97,23 @@ Depending on the request type, payload can be:
> > > > >       log offset: offset from start of supplied file descriptor
> > > > >           where logging starts (i.e. where guest address 0 would be 
> > > > > logged)
> > > > > + * An IOTLB message
> > > > > +   ---------------------------------------------------------
> > > > > +   | iova | size | user address | permissions flags | type |
> > > > > +   ---------------------------------------------------------
> > > > > +
> > > > > +   IOVA: a 64-bit guest I/O virtual address
> > > > guest -> VM
> > > Ok.
> > > 
> > > > > +   Size: a 64-bit size
> > > > How do you specify "all memory"? give special meaning to size 0?
> > > Good point, it does not support all memory currently.
> > > It is not vhost-user specific, but general to the vhost implementation.
> > But iommu needs it to support passthrough.
> 
> Probably not, we will just pass the mappings in vhost_memory_region to
> vhost. Its memory_size is also a __u64.
> 
> Thanks

That's different since that's chunks of qemu virtual memory.

IOMMU maps IOVA to GPA.

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MST