[Qemu-devel] [PATCH v3 15/17] ahci: add support for restarting non-queued commands

[John Snow <jsnow@redhat.com>]

From: Paolo Bonzini <pbonzini@redhat.com>

This is easy, since start_dma already restarts processing from the
beginning of the PRDT.

Migration is also easy to cover; the comment about busy_slot is
wrong, busy_slot will only be set if there is an error.  In this
case we have nothing to do really.  The core IDE code will restart
the operation and command list processing will proceed after the
erroring command has been completed.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: John Snow <jsnow@redhat.com>
---
 hw/ide/ahci.c | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/hw/ide/ahci.c b/hw/ide/ahci.c
index 3f4fc77..56a4867 100644
--- a/hw/ide/ahci.c
+++ b/hw/ide/ahci.c
@@ -1160,6 +1160,11 @@ static void ahci_start_dma(IDEDMA *dma, IDEState *s,
     dma_cb(s, 0);
 }
 
+static void ahci_restart_dma(IDEDMA *dma)
+{
+    /* Nothing to do, ahci_start_dma already resets s->io_buffer_offset.  */
+}
+
 /**
  * Called in DMA R/W chains to read the PRDT, utilizing ahci_populate_sglist.
  * Not currently invoked by PIO R/W chains,
@@ -1248,6 +1253,7 @@ static void ahci_irq_set(void *opaque, int n, int level)
 
 static const IDEDMAOps ahci_dma_ops = {
     .start_dma = ahci_start_dma,
+    .restart_dma = ahci_restart_dma,
     .start_transfer = ahci_start_transfer,
     .prepare_buf = ahci_dma_prepare_buf,
     .commit_buf = ahci_commit_buf,
@@ -1282,6 +1288,7 @@ void ahci_init(AHCIState *s, DeviceState *qdev, AddressSpace *as, int ports)
         ad->port_no = i;
         ad->port.dma = &ad->dma;
         ad->port.dma->ops = &ahci_dma_ops;
+        ide_register_restart_cb(&ad->port);
     }
 }
 
@@ -1360,16 +1367,16 @@ static int ahci_state_post_load(void *opaque, int version_id)
         map_page(s->as, &ad->res_fis,
                  ((uint64_t)pr->fis_addr_hi << 32) | pr->fis_addr, 256);
         /*
-         * All pending i/o should be flushed out on a migrate. However,
-         * we might not have cleared the busy_slot since this is done
-         * in a bh. Also, issue i/o against any slots that are pending.
+         * If an error is present, ad->busy_slot will be valid and not -1.
+         * In this case, an operation is waiting to resume and will re-check
+         * for additional AHCI commands to execute upon completion.
+         *
+         * In the case where no error was present, busy_slot will be -1,
+         * and we should check to see if there are additional commands waiting.
          */
-        if ((ad->busy_slot != -1) &&
-            !(ad->port.ifs[0].status & (BUSY_STAT|DRQ_STAT))) {
-            pr->cmd_issue &= ~(1 << ad->busy_slot);
-            ad->busy_slot = -1;
+        if (ad->busy_slot == -1) {
+            check_cmd(s, i);
         }
-        check_cmd(s, i);
     }
 
     return 0;
-- 
1.9.3