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


From: Jason Wang
Subject: Re: [Qemu-devel] [PATCH 6/6] spec/vhost-user spec: Add IOMMU support
Date: Mon, 15 May 2017 13:45:28 +0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0



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



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