From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: [PATCH RFC v8 00/11] vhost: ring format independence Date: Thu, 11 Jun 2020 07:34:14 -0400 Message-ID: <20200611113404.17810-1-mst@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" To: linux-kernel@vger.kernel.org Cc: netdev@vger.kernel.org, eperezma@redhat.com, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org List-Id: virtualization@lists.linuxfoundation.org This still causes corruption issues for people so don't try to use in production please. Posting to expedite debugging. This adds infrastructure required for supporting multiple ring formats. The idea is as follows: we convert descriptors to an independent format first, and process that converting to iov later. Used ring is similar: we fetch into an independent struct first, convert that to IOV later. The point is that we have a tight loop that fetches descriptors, which is good for cache utilization. This will also allow all kind of batching tricks - e.g. it seems possible to keep SMAP disabled while we are fetching multiple descriptors. For used descriptors, this allows keeping track of the buffer length without need to rescan IOV. This seems to perform exactly the same as the original code based on a microbenchmark. Lightly tested. More testing would be very much appreciated. changes from v8: - squashed in fixes. no longer hangs but still known to cause data corruption for some people. under debug. changes from v6: - fixes some bugs introduced in v6 and v5 changes from v5: - addressed comments by Jason: squashed API changes, fixed up discard changes from v4: - added used descriptor format independence - addressed comments by jason - fixed a crash detected by the lkp robot. changes from v3: - fixed error handling in case of indirect descriptors - add BUG_ON to detect buffer overflow in case of bugs in response to comment by Jason Wang - minor code tweaks Changes from v2: - fixed indirect descriptor batching reported by Jason Wang Changes from v1: - typo fixes Michael S. Tsirkin (14): vhost: option to fetch descriptors through an independent struct fixup! vhost: option to fetch descriptors through an independent struct Michael S. Tsirkin (11): vhost: option to fetch descriptors through an independent struct vhost: use batched get_vq_desc version vhost/net: pass net specific struct pointer vhost: reorder functions vhost: format-independent API for used buffers vhost/net: convert to new API: heads->bufs vhost/net: avoid iov length math vhost/test: convert to the buf API vhost/scsi: switch to buf APIs vhost/vsock: switch to the buf API vhost: drop head based APIs drivers/vhost/net.c | 174 +++++++++---------- drivers/vhost/scsi.c | 73 ++++---- drivers/vhost/test.c | 22 +-- drivers/vhost/vhost.c | 378 +++++++++++++++++++++++++++--------------- drivers/vhost/vhost.h | 44 +++-- drivers/vhost/vsock.c | 30 ++-- 6 files changed, 439 insertions(+), 282 deletions(-) -- MST