Commit Graph

3 Commits

Author SHA1 Message Date
Stefan Hajnoczi de0161c0d5 dataplane: handle misaligned virtio-blk requests
O_DIRECT on Linux has alignment requirements on I/O buffers and
misaligned requests result in -EINVAL.  The Linux virtio_blk guest
driver usually submits aligned requests so I forgot to handle misaligned
requests.

It turns out that virtio-win guest drivers submit misaligned requests.
Handle them using a bounce buffer that meets alignment requirements.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-01-14 10:06:57 +01:00
Stefan Hajnoczi b5ef1aab94 dataplane: extract virtio-blk read/write processing into do_rdwr_cmd()
Extract code for read/write command processing into do_rdwr_cmd().  This
brings together pieces that are spread across process_request().

The real motivation is to set the stage for handling misaligned
requests, which the next patch tackles.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2013-01-14 10:06:57 +01:00
Stefan Hajnoczi e72f66a0a2 dataplane: add virtio-blk data plane code
virtio-blk-data-plane is a subset implementation of virtio-blk.  It only
handles read, write, and flush requests.  It does this using a dedicated
thread that executes an epoll(2)-based event loop and processes I/O
using Linux AIO.

This approach performs very well but can be used for raw image files
only.  The number of IOPS achieved has been reported to be several times
higher than the existing virtio-blk implementation.

Eventually it should be possible to unify virtio-blk-data-plane with the
main body of QEMU code once the block layer and hardware emulation is
able to run outside the global mutex.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-01-02 16:08:47 +01:00