From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:55448) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dFzJ7-0006HK-Mt for qemu-devel@nongnu.org; Wed, 31 May 2017 04:48:46 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dFzJ4-00033T-Kk for qemu-devel@nongnu.org; Wed, 31 May 2017 04:48:45 -0400 Received: from mx1.redhat.com ([209.132.183.28]:35714) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dFzJ4-00033A-CG for qemu-devel@nongnu.org; Wed, 31 May 2017 04:48:42 -0400 References: <20170526142858.19931-1-maxime.coquelin@redhat.com> <20170526142858.19931-4-maxime.coquelin@redhat.com> <20170530210905-mutt-send-email-mst@kernel.org> From: Jason Wang Message-ID: <2503abfc-b0a4-16bb-e667-958ab7c571c1@redhat.com> Date: Wed, 31 May 2017 16:48:22 +0800 MIME-Version: 1.0 In-Reply-To: <20170530210905-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH v2 3/6] vhost: extend ring information update for IOTLB to all rings List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" , Maxime Coquelin Cc: yuanhan.liu@linux.intel.com, qemu-devel@nongnu.org, peterx@redhat.com, marcandre.lureau@gmail.com, wexu@redhat.com, vkaplans@redhat.com, jfreiman@redhat.com On 2017=E5=B9=B405=E6=9C=8831=E6=97=A5 02:12, Michael S. Tsirkin wrote: > On Fri, May 26, 2017 at 04:28:55PM +0200, Maxime Coquelin wrote: >> Vhost-kernel backend need > needs > >> to receive IOTLB entry for used ring >> information early, which is done by triggering a miss event on >> its address. >> >> This patch extends this behaviour to all rings information, to be >> compatible with vhost-user backend design. > Why does vhost-user need it though? > >> Signed-off-by: Maxime Coquelin >> --- >> v2: >> - Revert back to existing behaviour, i.e. only send IOTLB updates >> at ring enablement time, not at ring address setting time (mst). >> - Extend IOTLB misses to all ring addresses, not only used ring. >> >> hw/virtio/vhost.c | 8 ++++++-- >> 1 file changed, 6 insertions(+), 2 deletions(-) >> >> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c >> index 6eddb09..7867034 100644 >> --- a/hw/virtio/vhost.c >> +++ b/hw/virtio/vhost.c >> @@ -1552,11 +1552,15 @@ int vhost_dev_start(struct vhost_dev *hdev, Vi= rtIODevice *vdev) >> if (vhost_dev_has_iommu(hdev)) { >> hdev->vhost_ops->vhost_set_iotlb_callback(hdev, true); >> =20 >> - /* Update used ring information for IOTLB to work correctly, >> - * vhost-kernel code requires for this.*/ >> + /* >> + * Update rings information for IOTLB to work correctly, >> + * vhost-kernel and vhost-user codes require for this. > Better just say "Update ring info for vhost iotlb." > > The rest isn't really informative. > > > >> + */ >> for (i =3D 0; i < hdev->nvqs; ++i) { >> struct vhost_virtqueue *vq =3D hdev->vqs + i; >> vhost_device_iotlb_miss(hdev, vq->used_phys, true); >> + vhost_device_iotlb_miss(hdev, vq->desc_phys, true); >> + vhost_device_iotlb_miss(hdev, vq->avail_phys, true); > So I don't remember why does vhost in kernel want miss on used > at start time. > > Jason, could you comment on this please? In vhost_vq_init_access() we try to update used flags and fetch=20 last_used_idx, this requires we cache its translation in advance. We don't support IOTLB miss on control path (ioctl) now, so I choose to=20 update IOTLB. Thanks > > > >> } >> } >> return 0; >> --=20 >> 2.9.4