virtio-blk FUA write support has been introduced to the virtio spec [1], and a
kernel patch is under review [2]. This patch enables FUA on the virtio-blk
device, so guests can submit FUA writes instead of the slower alternative of a
regular write followed by a flush.

A simple randwrite fio workload on a RAM disk (bs=4k, iodepth=1, direct=1,
sync=1) shows a throughput improvement of 17.1k IOPS to 27.7k IOPS (+62%).

[1] https://lore.kernel.org/virtio-comment/20251112055113.62207-1-afaria@redhat.com/
[2] https://lore.kernel.org/linux-block/20261021055235.648957-1-afaria@redhat.com/

Alberto Faria (2):
  include: Add virtio-blk request flag FUA definitions
  virtio-blk: Add support for FUA write requests

 hw/block/virtio-blk.c                       | 27 +++++++++++++++++++++
 hw/core/machine.c                           |  1 +
 hw/virtio/virtio-qmp.c                      |  4 +++
 include/hw/virtio/virtio-blk.h              |  1 +
 include/standard-headers/linux/virtio_blk.h | 13 ++++++++--
 5 files changed, 44 insertions(+), 2 deletions(-)

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2.56.0