[Qemu-devel] [PATCH 05/10] dma-helpers: add dma_buf_read and dma_buf_write

[Paolo Bonzini <pbonzini@redhat.com>]

These helpers do a full transfer from an in-memory buffer to
target memory, with full support for MMIO areas.  It will be used to store
the reply of an emulated command into a QEMUSGList provided by the
adapter.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 cutils.c      |    8 +++---
 dma-helpers.c |   63 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 dma.h         |    5 ++++
 3 files changed, 72 insertions(+), 4 deletions(-)

diff --git a/cutils.c b/cutils.c
index f9a7e36..969fd2e 100644
--- a/cutils.c
+++ b/cutils.c
@@ -215,14 +215,14 @@ void qemu_iovec_concat(QEMUIOVector *dst, QEMUIOVector *src, size_t size)
 
 void qemu_iovec_destroy(QEMUIOVector *qiov)
 {
-    assert(qiov->nalloc != -1);
-
-    qemu_free(qiov->iov);
+    if (qiov->nalloc != -1) {
+        qemu_free(qiov->iov);
+    }
 }
 
 void qemu_iovec_reset(QEMUIOVector *qiov)
 {
-    assert(qiov->nalloc != -1);
+    assert(qiov->nalloc != -1 || qiov->niov == 0);
 
     qiov->niov = 0;
     qiov->size = 0;
diff --git a/dma-helpers.c b/dma-helpers.c
index 4469ce2..10dc8ca 100644
--- a/dma-helpers.c
+++ b/dma-helpers.c
@@ -84,6 +84,7 @@ struct DMAAIOCB {
     BlockDriverAIOCB common;
     union {
         BlockDriverState *bs;
+        uint8_t *ptr;
     } u;
     BlockDriverAIOCB *acb;
     QEMUSGList *sg;
@@ -245,3 +246,65 @@ BlockDriverAIOCB *dma_bdrv_write(BlockDriverState *bs,
 {
     return dma_bdrv_io(bs, sg, sector, bdrv_aio_writev, cb, opaque, 1);
 }
+
+
+static int dma_copy_cb(DMAAIOCB *dbs, int ret)
+{
+    void *mem;
+    target_phys_addr_t cur_len;
+
+    assert(ret == 0);
+
+    /* sector_num is the residual number of bytes to copy.  */
+    while (dbs->sector_num > 0 &&
+           (mem = qemu_sglist_map_segment(dbs->sg, &cur_len,
+                                          !dbs->is_write)) != NULL) {
+        if (dbs->is_write) {
+            memcpy(dbs->u.ptr, mem, cur_len);
+        } else {
+            memcpy(mem, dbs->u.ptr, cur_len);
+        }
+        cpu_physical_memory_unmap(mem, cur_len, !dbs->is_write, cur_len);
+        dbs->u.ptr += cur_len;
+        dbs->sector_num -= cur_len;
+    }
+
+    if (dbs->sg->resid > 0) {
+        cpu_register_map_client(dbs, continue_after_map_failure);
+        return -EAGAIN;
+    }
+
+    return 0;
+}
+
+static BlockDriverAIOCB *dma_copy(
+    uint8_t *ptr, int32_t len, QEMUSGList *sg,
+    void (*cb)(void *opaque, int ret), void *opaque, int is_write)
+{
+    DMAAIOCB *dbs =  qemu_aio_get(&dma_aio_pool, NULL, cb, opaque);
+
+    dbs->acb = NULL;
+    dbs->u.ptr = ptr;
+    dbs->sg = sg;
+    dbs->sector_num = MIN(len, sg->size);
+    dbs->is_write = is_write;
+    dbs->bh = NULL;
+    dbs->cb = dma_copy_cb;
+    qemu_iovec_init_external(&dbs->iov, NULL, 0);
+    qemu_sglist_rewind(sg);
+    return dma_continue(dbs, 0);
+}
+
+BlockDriverAIOCB *dma_buf_read(
+    uint8_t *ptr, int32_t len, QEMUSGList *sg,
+    void (*cb)(void *opaque, int ret), void *opaque)
+{
+    return dma_copy(ptr, len, sg, cb, opaque, 0);
+}
+
+BlockDriverAIOCB *dma_buf_write(
+    uint8_t *ptr, int32_t len, QEMUSGList *sg,
+    void (*cb)(void *opaque, int ret), void *opaque)
+{
+    return dma_copy(ptr, len, sg, cb, opaque, 1);
+}
diff --git a/dma.h b/dma.h
index 363e932..6bf51ee 100644
--- a/dma.h
+++ b/dma.h
@@ -58,4 +58,9 @@ BlockDriverAIOCB *dma_bdrv_read(BlockDriverState *bs,
 BlockDriverAIOCB *dma_bdrv_write(BlockDriverState *bs,
                                  QEMUSGList *sg, uint64_t sector,
                                  BlockDriverCompletionFunc *cb, void *opaque);
+BlockDriverAIOCB *dma_buf_read(uint8_t *ptr, int32_t len, QEMUSGList *sg,
+                               BlockDriverCompletionFunc *cb, void *opaque);
+BlockDriverAIOCB *dma_buf_write(uint8_t *ptr, int32_t len, QEMUSGList *sg,
+                                BlockDriverCompletionFunc *cb, void *opaque);
+
 #endif
-- 
1.7.6