[PATCH v2 0/5] virtio: drop sizing vqs during init

From: "Michael S. Tsirkin" <mst@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: Jens Axboe <axboe@kernel.dk>,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	netdev@vger.kernel.org,
	virtualization@lists.linux-foundation.org,
	James Bottomley <James.Bottomley@hansenpartnership.com>,
	Eric Dumazet <edumazet@google.com>,
	Greg KH <gregkh@linuxfoundation.org>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	"David S. Miller" <davem@davemloft.net>,
	Guenter Roeck <linux@roeck-us.net>
Subject: [PATCH v2 0/5] virtio: drop sizing vqs during init
Date: Mon, 15 Aug 2022 17:53:14 -0400	[thread overview]
Message-ID: <20220815215251.154451-1-mst@redhat.com> (raw)

Supplying size during init does not work for all transports.
In fact for legacy pci doing that causes a memory
corruption which was reported on Google Cloud.

We might get away with changing size to size_hint so it's
safe to ignore and then fixing legacy to ignore the hint.

But the benefit is unclear in any case, so let's revert for now.
Any new version will have to come with
- documentation of performance gains
- performance testing showing existing workflows
  are not harmed materially. especially ones with
  bursty traffic
- report of testing on legacy devices

Huge shout out to Andres Freund for the effort spent reproducing and
debugging!  Thanks to Guenter Roeck for help with testing!

Michael S. Tsirkin (5):
  virtio_net: Revert "virtio_net: set the default max ring size by
    find_vqs()"
  virtio: Revert "virtio: add helper virtio_find_vqs_ctx_size()"
  virtio-mmio: Revert "virtio_mmio: support the arg sizes of find_vqs()"
  virtio_pci: Revert "virtio_pci: support the arg sizes of find_vqs()"
  virtio: Revert "virtio: find_vqs() add arg sizes"

 arch/um/drivers/virtio_uml.c             |  2 +-
 drivers/net/virtio_net.c                 | 42 +++---------------------
 drivers/platform/mellanox/mlxbf-tmfifo.c |  1 -
 drivers/remoteproc/remoteproc_virtio.c   |  1 -
 drivers/s390/virtio/virtio_ccw.c         |  1 -
 drivers/virtio/virtio_mmio.c             |  9 ++---
 drivers/virtio/virtio_pci_common.c       | 20 +++++------
 drivers/virtio/virtio_pci_common.h       |  3 +-
 drivers/virtio/virtio_pci_legacy.c       |  6 +---
 drivers/virtio/virtio_pci_modern.c       | 17 +++-------
 drivers/virtio/virtio_vdpa.c             |  1 -
 include/linux/virtio_config.h            | 26 +++------------
 12 files changed, 28 insertions(+), 101 deletions(-)

-- 
MST

_______________________________________________
Virtualization mailing list
Virtualization@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/virtualization