Merge remote-tracking branch 'remotes/stefanha/tags/block-pull-request' into staging

Pull request

# gpg: Signature made Fri 22 Feb 2019 14:07:01 GMT
# gpg:                using RSA key 9CA4ABB381AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>" [full]
# gpg:                 aka "Stefan Hajnoczi <stefanha@gmail.com>" [full]
# Primary key fingerprint: 8695 A8BF D3F9 7CDA AC35  775A 9CA4 ABB3 81AB 73C8

* remotes/stefanha/tags/block-pull-request: (27 commits)
  tests/virtio-blk: add test for DISCARD command
  tests/virtio-blk: add test for WRITE_ZEROES command
  tests/virtio-blk: add virtio_blk_fix_dwz_hdr() function
  tests/virtio-blk: change assert on data_size in virtio_blk_request()
  virtio-blk: add DISCARD and WRITE_ZEROES features
  virtio-blk: set config size depending on the features enabled
  virtio-net: make VirtIOFeature usable for other virtio devices
  virtio-blk: add "discard" and "write-zeroes" properties
  virtio-blk: add host_features field in VirtIOBlock
  virtio-blk: add acct_failed param to virtio_blk_handle_rw_error()
  hw/ide: drop iov field from IDEDMA
  hw/ide: drop iov field from IDEBufferedRequest
  hw/ide: drop iov field from IDEState
  tests/test-bdrv-drain: use QEMU_IOVEC_INIT_BUF
  migration/block: use qemu_iovec_init_buf
  qemu-img: use qemu_iovec_init_buf
  block/vmdk: use qemu_iovec_init_buf
  block/qed: use qemu_iovec_init_buf
  block/qcow2: use qemu_iovec_init_buf
  block/qcow: use qemu_iovec_init_buf
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 62 insertions, 2 deletions

diff --git a/include/qemu/iov.h b/include/qemu/iov.h
index 5f433c7..48b4598 100644
--- a/include/qemu/iov.h
+++ b/include/qemu/iov.h
@@ -133,10 +133,70 @@ size_t iov_discard_back(struct iovec *iov, unsigned int *iov_cnt,
 typedef struct QEMUIOVector {
     struct iovec *iov;
     int niov;
-    int nalloc;
-    size_t size;
+
+    /*
+     * For external @iov (qemu_iovec_init_external()) or allocated @iov
+     * (qemu_iovec_init()), @size is the cumulative size of iovecs and
+     * @local_iov is invalid and unused.
+     *
+     * For embedded @iov (QEMU_IOVEC_INIT_BUF() or qemu_iovec_init_buf()),
+     * @iov is equal to &@local_iov, and @size is valid, as it has same
+     * offset and type as @local_iov.iov_len, which is guaranteed by
+     * static assertion below.
+     *
+     * @nalloc is always valid and is -1 both for embedded and external
+     * cases. It is included in the union only to ensure the padding prior
+     * to the @size field will not result in a 0-length array.
+     */
+    union {
+        struct {
+            int nalloc;
+            struct iovec local_iov;
+        };
+        struct {
+            char __pad[sizeof(int) + offsetof(struct iovec, iov_len)];
+            size_t size;
+        };
+    };
 } QEMUIOVector;
 
+QEMU_BUILD_BUG_ON(offsetof(QEMUIOVector, size) !=
+                  offsetof(QEMUIOVector, local_iov.iov_len));
+
+#define QEMU_IOVEC_INIT_BUF(self, buf, len)              \
+{                                                        \
+    .iov = &(self).local_iov,                            \
+    .niov = 1,                                           \
+    .nalloc = -1,                                        \
+    .local_iov = {                                       \
+        .iov_base = (void *)(buf), /* cast away const */ \
+        .iov_len = (len),                                \
+    },                                                   \
+}
+
+/*
+ * qemu_iovec_init_buf
+ *
+ * Initialize embedded QEMUIOVector.
+ *
+ * Note: "const" is used over @buf pointer to make it simple to pass
+ * const pointers, appearing in read functions. Then this "const" is
+ * cast away by QEMU_IOVEC_INIT_BUF().
+ */
+static inline void qemu_iovec_init_buf(QEMUIOVector *qiov,
+                                       const void *buf, size_t len)
+{
+    *qiov = (QEMUIOVector) QEMU_IOVEC_INIT_BUF(*qiov, buf, len);
+}
+
+static inline void *qemu_iovec_buf(QEMUIOVector *qiov)
+{
+    /* Only supports embedded iov */
+    assert(qiov->nalloc == -1 && qiov->iov == &qiov->local_iov);
+
+    return qiov->local_iov.iov_base;
+}
+
 void qemu_iovec_init(QEMUIOVector *qiov, int alloc_hint);
 void qemu_iovec_init_external(QEMUIOVector *qiov, struct iovec *iov, int niov);
 void qemu_iovec_add(QEMUIOVector *qiov, void *base, size_t len);