commit 827805a2492c1bbf1c0712ed18ee069b4ebf3dd6
author Fam Zheng <famz@redhat.com> Wed Jun 11 12:11:48 2014 +0800
committer Kevin Wolf <kwolf@redhat.com> Fri Jun 27 18:18:25 2014 +0200
tree 879b2006b295fb99e4f545d3ddde0fb3eb1c2efc
parent eddb102e86f61d4b71877f8ac268ebc4bf7265bf

virtio-blk: Convert VirtIOBlockReq.out to structrue

The virtio code currently assumes that the outhdr is in its own iovec.
This is not guaranteed by the spec, so we should relax this assumption.

Convert the VirtIOBlockReq.out field to structrue so that we can use
iov_to_buf and then discard the header from the beginning of iovec.

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

hw/block/virtio-blk.c

diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index b5cc385..0561095 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -12,6 +12,7 @@
  */
 
 #include "qemu-common.h"
+#include "qemu/iov.h"
 #include "qemu/error-report.h"
 #include "trace.h"
 #include "hw/block/block.h"
@@ -81,7 +82,7 @@
     trace_virtio_blk_rw_complete(req, ret);
 
     if (ret) {
-        bool is_read = !(ldl_p(&req->out->type) & VIRTIO_BLK_T_OUT);
+        bool is_read = !(ldl_p(&req->out.type) & VIRTIO_BLK_T_OUT);
         if (virtio_blk_handle_rw_error(req, -ret, is_read))
             return;
     }
@@ -287,7 +288,7 @@
     BlockRequest *blkreq;
     uint64_t sector;
 
-    sector = ldq_p(&req->out->sector);
+    sector = ldq_p(&req->out.sector);
 
     bdrv_acct_start(req->dev->bs, &req->acct, req->qiov.size, BDRV_ACCT_WRITE);
 
@@ -321,7 +322,7 @@
 {
     uint64_t sector;
 
-    sector = ldq_p(&req->out->sector);
+    sector = ldq_p(&req->out.sector);
 
     bdrv_acct_start(req->dev->bs, &req->acct, req->qiov.size, BDRV_ACCT_READ);
 
@@ -344,22 +345,29 @@
     MultiReqBuffer *mrb)
 {
     uint32_t type;
+    struct iovec *iov = req->elem->out_sg;
+    unsigned out_num = req->elem->out_num;
 
     if (req->elem->out_num < 1 || req->elem->in_num < 1) {
         error_report("virtio-blk missing headers");
         exit(1);
     }
 
-    if (req->elem->out_sg[0].iov_len < sizeof(*req->out) ||
+    if (req->elem->out_sg[0].iov_len < sizeof(req->out) ||
         req->elem->in_sg[req->elem->in_num - 1].iov_len < sizeof(*req->in)) {
         error_report("virtio-blk header not in correct element");
         exit(1);
     }
 
-    req->out = (void *)req->elem->out_sg[0].iov_base;
+    if (unlikely(iov_to_buf(iov, out_num, 0, &req->out,
+                            sizeof(req->out)) != sizeof(req->out))) {
+        error_report("virtio-blk request outhdr too short");
+        exit(1);
+    }
+    iov_discard_front(&iov, &out_num, sizeof(req->out));
     req->in = (void *)req->elem->in_sg[req->elem->in_num - 1].iov_base;
 
-    type = ldl_p(&req->out->type);
+    type = ldl_p(&req->out.type);
 
     if (type & VIRTIO_BLK_T_FLUSH) {
         virtio_blk_handle_flush(req, mrb);

include/hw/virtio/virtio-blk.h

diff --git a/include/hw/virtio/virtio-blk.h b/include/hw/virtio/virtio-blk.h
index b495e42..2571e96 100644
--- a/include/hw/virtio/virtio-blk.h
+++ b/include/hw/virtio/virtio-blk.h
@@ -138,7 +138,7 @@
     VirtIOBlock *dev;
     VirtQueueElement *elem;
     struct virtio_blk_inhdr *in;
-    struct virtio_blk_outhdr *out;
+    struct virtio_blk_outhdr out;
     QEMUIOVector qiov;
     struct VirtIOBlockReq *next;
     BlockAcctCookie acct;