From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51776) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cxvjB-0003Zh-Dt for qemu-devel@nongnu.org; Tue, 11 Apr 2017 09:21:05 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cxvj8-0007xe-8N for qemu-devel@nongnu.org; Tue, 11 Apr 2017 09:21:01 -0400 Received: from mx1.redhat.com ([209.132.183.28]:57296) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cxvj8-0007xV-02 for qemu-devel@nongnu.org; Tue, 11 Apr 2017 09:20:58 -0400 Date: Tue, 11 Apr 2017 21:20:46 +0800 From: Peter Xu Message-ID: <20170411132046.GA16464@pxdev.xzpeter.org> References: <20170411101002.28451-1-maxime.coquelin@redhat.com> <20170411101002.28451-3-maxime.coquelin@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20170411101002.28451-3-maxime.coquelin@redhat.com> Subject: Re: [Qemu-devel] [RFC 2/2] spec/vhost-user spec: Add IOMMU support List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Maxime Coquelin Cc: mst@redhat.com, vkaplans@redhat.com, jasowang@redhat.com, wexu@redhat.com, yuanhan.liu@linux.intel.com, virtio-comment@lists.oasis-open.org, qemu-devel@nongnu.org On Tue, Apr 11, 2017 at 12:10:02PM +0200, Maxime Coquelin wrote: > This patch specifies the master/slave communication to support > device IOTLB implementation 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 > --- > docs/specs/vhost-user.txt | 56 +++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 56 insertions(+) > > diff --git a/docs/specs/vhost-user.txt b/docs/specs/vhost-user.txt > index b365047..048a4d6 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 > + Size: a 64-bit size > + User address: a 64-bit user address > + Permissions flags: a 8-bit bit field: > + - Bit 0: Read access > + - Bit 1: Write access > + Type: a 8-bit IOTLB message type: > + - 1: IOTLB miss > + - 2: IOTLB update > + - 3: IOTLB invalidate > + - 4: IOTLB access fail > + > In QEMU the vhost-user message is implemented with the following struct: > > typedef struct VhostUserMsg { > @@ -109,6 +126,7 @@ typedef struct VhostUserMsg { > struct vhost_vring_addr addr; > VhostUserMemory memory; > VhostUserLog log; > + struct vhost_iotlb_msg iotlb; > }; > } QEMU_PACKED VhostUserMsg; > > @@ -258,6 +276,30 @@ Once the source has finished migration, rings will be stopped by > the source. No further update must be done before rings are > restarted. > > +IOMMU support > +------------- > + > +When the VIRTIO_F_IOMMU_PLATFORM feature has been negotiated, the master has > +to send IOTLB entries update & invalidation by sending VHOST_USER_IOTLB_MSG > +requests to the slave with a struct vhost_iotlb_msg payload. For update events, > +the iotlb payload has to be filled with the update message type (2), the I/O > +virtual address, the size, the user virtual address, and the permissions > +flags. For invalidation events, the iotlb payload has to be filled with the > +update message type (3), the I/O virtual address and the size. On success, the s/update/invalidate/? > +slave is expected to reply with a zero payload, non-zero otherwise. Is this ack mechanism really necessary? If not, not sure it'll be nice to keep vhost-user/vhost-kernel aligned on this behavior. At least that'll simplify vhost-user implementation on QEMU side (iiuc even without introducing new functions for update/invalidate operations). > + > +When the VHOST_USER_PROTOCOL_F_SLAVE_REQ is supported by the slave, and the > +master initiated the slave to master communication channel using the > +VHOST_USER_SET_SLAVE_REQ_FD request, the slave can send IOTLB miss and access > +failure events by sending VHOST_USER_IOTLB_MSG requests to the master with a > +struct vhost_iotlb_msg payload. For miss events, the iotlb payload has to be > +filled with the miss message type (1), the I/O virtual address and the > +permissions flags. For access failure event, the iotlb payload has to be > +filled with the access failure message type (4), the I/O virtual address and > +the permissions flags. On success, the master is expected to reply when the > +request has been handled (for example, on miss requests, once the device IOTLB > +has been updated) with a zero payload, non-zero otherwise. Failed to understand the last sentence clearly. IIUC vhost-net will reply with an UPDATE message when a MISS message is received. Here for vhost-user are we going to send one extra zero payload after that? > + > Protocol features > ----------------- > > @@ -524,6 +566,20 @@ Message types > has been negotiated, and protocol feature bit VHOST_USER_PROTOCOL_F_SLAVE_REQ > bit is present in VHOST_USER_GET_PROTOCOL_FEATURES. > > + * VHOST_USER_IOTLB_MSG > + > + Id: 22 > + Equivalent ioctl: N/A (equivalent to VHOST_IOTLB_MSG message type) > + Initiator: Master or slave > + > + Send IOTLB messages with struct vhost_iotlb_msg as payload. > + Master sends such requests to update and invalidate entries in the device > + IOTLB. Slave sends such requests to notify of an IOTLB miss, or an IOTLB s/of//? > + access failure. The recipient has to acknowledge the request with > + sending zero as u64 payload for success, non-zero otherwise. Same question here... Thanks, > + This request should be send only when VIRTIO_F_IOMMU_PLATFORM feature > + has been successfully negotiated. > + > VHOST_USER_PROTOCOL_F_REPLY_ACK: > ------------------------------- > The original vhost-user specification only demands replies for certain > -- > 2.9.3 > -- Peter Xu