From 3a1ed0ed9dff3a7349053a529a082aa69cb96ad1 Mon Sep 17 00:00:00 2001
Message-Id: <3a1ed0ed9dff3a7349053a529a082aa69cb96ad1.1358333973.git.minovotn@redhat.com>
In-Reply-To: <fc8dd14f2112bcd239ef87c2b60d93e174e17cd3.1358333973.git.minovotn@redhat.com>
References: <fc8dd14f2112bcd239ef87c2b60d93e174e17cd3.1358333973.git.minovotn@redhat.com>
From: Stefan Hajnoczi <stefanha@redhat.com>
Date: Mon, 14 Jan 2013 15:00:15 +0100
Subject: [PATCH 3/3] dataplane: handle misaligned virtio-blk requests
RH-Author: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: <1358175615-24929-4-git-send-email-stefanha@redhat.com>
Patchwork-id: 45783
O-Subject: [RHEL-6.4 qemu-kvm PATCH 3/3] dataplane: handle misaligned virtio-blk requests
Bugzilla: 895392
RH-Acked-by: Kevin Wolf <kwolf@redhat.com>
RH-Acked-by: Laszlo Ersek <lersek@redhat.com>
RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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>
(cherry picked from commit de0161c0d553f2aaf6118ca87f978a5e6b4a9732)
Conflicts:
hw/dataplane/virtio-blk.c:
qemu_iovec_from_buf() -> qemu_iovec_from_buffer()
qemu_iovec_to_buf() -> qemu_iovec_to_buffer()
g_slice_alloc() -> qemu_malloc()
g_slice_free() -> qemu_free()
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
hw/dataplane/virtio-blk.c | 40 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 40 insertions(+)
Signed-off-by: Michal Novotny <minovotn@redhat.com>
---
hw/dataplane/virtio-blk.c | 40 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 40 insertions(+)
diff --git a/hw/dataplane/virtio-blk.c b/hw/dataplane/virtio-blk.c
index d706b24..7703370 100644
--- a/hw/dataplane/virtio-blk.c
+++ b/hw/dataplane/virtio-blk.c
@@ -34,6 +34,8 @@ typedef struct {
struct iocb iocb; /* Linux AIO control block */
QEMUIOVector *inhdr; /* iovecs for virtio_blk_inhdr */
unsigned int head; /* vring descriptor index */
+ struct iovec *bounce_iov; /* used if guest buffers are unaligned */
+ QEMUIOVector *read_qiov; /* for read completion /w bounce buffer */
} VirtIOBlockRequest;
struct VirtIOBlockDataPlane {
@@ -87,6 +89,18 @@ static void complete_request(struct iocb *iocb, ssize_t ret, void *opaque)
trace_virtio_blk_data_plane_complete_request(s, req->head, ret);
+ if (req->read_qiov) {
+ assert(req->bounce_iov);
+ qemu_iovec_from_buffer(req->read_qiov, req->bounce_iov->iov_base, len);
+ qemu_iovec_destroy(req->read_qiov);
+ qemu_free(req->read_qiov);
+ }
+
+ if (req->bounce_iov) {
+ qemu_vfree(req->bounce_iov->iov_base);
+ qemu_free(req->bounce_iov);
+ }
+
qemu_iovec_from_buffer(req->inhdr, &hdr, sizeof(hdr));
qemu_iovec_destroy(req->inhdr);
qemu_free(req->inhdr);
@@ -134,6 +148,30 @@ static int do_rdwr_cmd(VirtIOBlockDataPlane *s, bool read,
QEMUIOVector *inhdr)
{
struct iocb *iocb;
+ QEMUIOVector qiov;
+ struct iovec *bounce_iov = NULL;
+ QEMUIOVector *read_qiov = NULL;
+
+ qemu_iovec_init_external(&qiov, iov, iov_cnt);
+ if (!bdrv_qiov_is_aligned(s->blk->conf.bs, &qiov)) {
+ void *bounce_buffer = qemu_blockalign(s->blk->conf.bs, qiov.size);
+
+ if (read) {
+ /* Need to copy back from bounce buffer on completion */
+ read_qiov = qemu_malloc(sizeof(*read_qiov));
+ qemu_iovec_init(read_qiov, iov_cnt);
+ qemu_iovec_concat_iov(read_qiov, iov, iov_cnt, 0, qiov.size);
+ } else {
+ qemu_iovec_to_buffer(&qiov, bounce_buffer);
+ }
+
+ /* Redirect I/O to aligned bounce buffer */
+ bounce_iov = qemu_malloc(sizeof(*bounce_iov));
+ bounce_iov->iov_base = bounce_buffer;
+ bounce_iov->iov_len = qiov.size;
+ iov = bounce_iov;
+ iov_cnt = 1;
+ }
iocb = ioq_rdwr(&s->ioqueue, read, iov, iov_cnt, offset);
@@ -141,6 +179,8 @@ static int do_rdwr_cmd(VirtIOBlockDataPlane *s, bool read,
VirtIOBlockRequest *req = container_of(iocb, VirtIOBlockRequest, iocb);
req->head = head;
req->inhdr = inhdr;
+ req->bounce_iov = bounce_iov;
+ req->read_qiov = read_qiov;
return 0;
}
--
1.7.11.7