--- qemu/hw/ide/pci.c	2018/04/24 17:40:36	1.1.1.1
+++ qemu/hw/ide/pci.c	2018/04/24 18:30:53	1.1.1.2
@@ -40,8 +40,27 @@ void bmdma_cmd_writeb(void *opaque, uint
     printf("%s: 0x%08x\n", __func__, val);
 #endif
     if (!(val & BM_CMD_START)) {
-        /* XXX: do it better */
-        ide_dma_cancel(bm);
+        /*
+         * We can't cancel Scatter Gather DMA in the middle of the
+         * operation or a partial (not full) DMA transfer would reach
+         * the storage so we wait for completion instead (we beahve
+         * like if the DMA was completed by the time the guest trying
+         * to cancel dma with bmdma_cmd_writeb with BM_CMD_START not
+         * set).
+         *
+         * In the future we'll be able to safely cancel the I/O if the
+         * whole DMA operation will be submitted to disk with a single
+         * aio operation with preadv/pwritev.
+         */
+        if (bm->aiocb) {
+            qemu_aio_flush();
+#ifdef DEBUG_IDE
+            if (bm->aiocb)
+                printf("ide_dma_cancel: aiocb still pending");
+            if (bm->status & BM_STATUS_DMAING)
+                printf("ide_dma_cancel: BM_STATUS_DMAING still pending");
+#endif
+        }
         bm->cmd = val & 0x09;
     } else {
         if (!(bm->status & BM_STATUS_DMAING)) {
@@ -121,6 +140,28 @@ void bmdma_addr_writel(void *opaque, uin
     bm->cur_addr = bm->addr;
 }
 
+static bool ide_bmdma_current_needed(void *opaque)
+{
+    BMDMAState *bm = opaque;
+
+    return (bm->cur_prd_len != 0);
+}
+
+static const VMStateDescription vmstate_bmdma_current = {
+    .name = "ide bmdma_current",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .minimum_version_id_old = 1,
+    .fields      = (VMStateField []) {
+        VMSTATE_UINT32(cur_addr, BMDMAState),
+        VMSTATE_UINT32(cur_prd_last, BMDMAState),
+        VMSTATE_UINT32(cur_prd_addr, BMDMAState),
+        VMSTATE_UINT32(cur_prd_len, BMDMAState),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
+
 static const VMStateDescription vmstate_bmdma = {
     .name = "ide bmdma",
     .version_id = 3,
@@ -134,6 +175,14 @@ static const VMStateDescription vmstate_
         VMSTATE_UINT32(nsector, BMDMAState),
         VMSTATE_UINT8(unit, BMDMAState),
         VMSTATE_END_OF_LIST()
+    },
+    .subsections = (VMStateSubsection []) {
+        {
+            .vmsd = &vmstate_bmdma_current,
+            .needed = ide_bmdma_current_needed,
+        }, {
+            /* empty */
+        }
     }
 };