From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [PATCH 0/6] vhost: Reset batched descriptors on SET_VRING_BASE call Date: Sun, 29 Mar 2020 07:49:23 -0400 Message-ID: <20200329074023-mutt-send-email-mst@kernel.org> References: <20200329113359.30960-1-eperezma@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Return-path: Content-Disposition: inline In-Reply-To: <20200329113359.30960-1-eperezma@redhat.com> Sender: kvm-owner@vger.kernel.org To: Eugenio =?iso-8859-1?Q?P=E9rez?= Cc: "virtualization@lists.linux-foundation.org" , Halil Pasic , Stephen Rothwell , Linux Next Mailing List , kvm list , Cornelia Huck , Christian Borntraeger , "linux-kernel@vger.kernel.org" List-Id: virtualization@lists.linuxfoundation.org On Sun, Mar 29, 2020 at 01:33:53PM +0200, Eugenio Pérez wrote: > Vhost did not reset properly the batched descriptors on SET_VRING_BASE event. Because of that, is possible to return an invalid descriptor to the guest. > This series ammend this, and creates a test to assert correct behavior. To do that, they need to expose a new function in virtio_ring, virtqueue_reset_free_head. Not sure if this can be avoided. Question: why not reset the batch when private_data changes? At the moment both net and scsi poke at private data directly, if they do this through a wrapper we can use that to 1. check that vq mutex is taken properly 2. reset batching This seems like a slightly better API > > Also, change from https://lkml.org/lkml/2020/3/27/108 is not included, that avoids to update a variable in a loop where it can be updated once. > > This is meant to be applied on top of eccb852f1fe6bede630e2e4f1a121a81e34354ab in git.kernel.org/pub/scm/linux/kernel/git/mst/vhost.git, and some commits should be squashed with that series. Thanks a lot! I'll apply this for now so Christian can start testing, but I'd like the comment above addressed before I push this to Linus. > Eugenio Pérez (6): > tools/virtio: Add --batch option > tools/virtio: Add --batch=random option > tools/virtio: Add --reset=random > tools/virtio: Make --reset reset ring idx > vhost: Delete virtqueue batch_descs member > fixup! vhost: batching fetches > > drivers/vhost/test.c | 57 ++++++++++++++++ > drivers/vhost/test.h | 1 + > drivers/vhost/vhost.c | 12 +++- > drivers/vhost/vhost.h | 1 - > drivers/virtio/virtio_ring.c | 18 +++++ > include/linux/virtio.h | 2 + > tools/virtio/linux/virtio.h | 2 + > tools/virtio/virtio_test.c | 123 +++++++++++++++++++++++++++++++---- > 8 files changed, 201 insertions(+), 15 deletions(-) > > -- > 2.18.1