[Qemu-devel] [PATCH 2/2] ide: unify io_buffer_offset increments

[John Snow <jsnow@redhat.com>]

This variable was originally added to keep track of offsets in AHCI
rather exclusively, but it was added to IDEState. AHCI fakes all PIO
transfers using DMA and a scatter-gather list. When the core or atapi
layers invoke HBA-specific mechanisms for transfers, they do not always
know that it is being backed by DMA or a sglist, so this offset is not
always updated by all the code everywhere.

If we modify it in dma_buf_commit, however, any HBA that needs to use
this offset to manage operating on only part of a sglist will have
access to it.

As a result, this will fix ATAPI PIO transfers performed through the AHCI
HBA, which were previously not modifying this value appropriately. This
should fix AHCI/ATAPI with OVMF, which tries to use these PIO transfers.

Reported-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: John Snow <jsnow@redhat.com>
---
 hw/ide/ahci.c     | 22 +++++++---------------
 hw/ide/core.c     |  5 ++---
 hw/ide/internal.h |  1 +
 3 files changed, 10 insertions(+), 18 deletions(-)

diff --git a/hw/ide/ahci.c b/hw/ide/ahci.c
index bb6a92f..15427f4 100644
--- a/hw/ide/ahci.c
+++ b/hw/ide/ahci.c
@@ -50,7 +50,6 @@ static void ahci_reset_port(AHCIState *s, int port);
 static void ahci_write_fis_d2h(AHCIDevice *ad, uint8_t *cmd_fis);
 static void ahci_init_d2h(AHCIDevice *ad);
 static int ahci_dma_prepare_buf(IDEDMA *dma, int32_t limit);
-static void ahci_commit_buf(IDEDMA *dma, uint32_t tx_bytes);
 static bool ahci_map_clb_address(AHCIDevice *ad);
 static bool ahci_map_fis_address(AHCIDevice *ad);
 static void ahci_unmap_clb_address(AHCIDevice *ad);
@@ -1285,7 +1284,7 @@ out:
     s->data_ptr = s->data_end;
 
     /* Update number of transferred bytes, destroy sglist */
-    ahci_commit_buf(dma, size);
+    dma_buf_commit(s, size);
 
     s->end_transfer_func(s);
 
@@ -1327,9 +1326,8 @@ static void ahci_restart(IDEDMA *dma)
 }
 
 /**
- * Called in DMA R/W chains to read the PRDT, utilizing ahci_populate_sglist.
- * Not currently invoked by PIO R/W chains,
- * which invoke ahci_populate_sglist via ahci_start_transfer.
+ * Called in DMA and PIO R/W chains to read the PRDT.
+ * Not shared with NCQ pathways.
  */
 static int32_t ahci_dma_prepare_buf(IDEDMA *dma, int32_t limit)
 {
@@ -1348,21 +1346,16 @@ static int32_t ahci_dma_prepare_buf(IDEDMA *dma, int32_t limit)
 }
 
 /**
- * Destroys the scatter-gather list,
- * and updates the command header with a bytes-read value.
- * called explicitly via ahci_dma_rw_buf (ATAPI DMA),
- * and ahci_start_transfer (PIO R/W),
- * and called via callback from ide_dma_cb for DMA R/W paths.
+ * Updates the command header with a bytes-read value.
+ * Called via dma_buf_commit, for both DMA and PIO paths.
+ * sglist destruction is handled within dma_buf_commit.
  */
 static void ahci_commit_buf(IDEDMA *dma, uint32_t tx_bytes)
 {
     AHCIDevice *ad = DO_UPCAST(AHCIDevice, dma, dma);
-    IDEState *s = &ad->port.ifs[0];
 
     tx_bytes += le32_to_cpu(ad->cur_cmd->status);
     ad->cur_cmd->status = cpu_to_le32(tx_bytes);
-
-    qemu_sglist_destroy(&s->sg);
 }
 
 static int ahci_dma_rw_buf(IDEDMA *dma, int is_write)
@@ -1383,10 +1376,9 @@ static int ahci_dma_rw_buf(IDEDMA *dma, int is_write)
     }
 
     /* free sglist, update byte count */
-    ahci_commit_buf(dma, l);
+    dma_buf_commit(s, l);
 
     s->io_buffer_index += l;
-    s->io_buffer_offset += l;
 
     DPRINTF(ad->port_no, "len=%#x\n", l);
 
diff --git a/hw/ide/core.c b/hw/ide/core.c
index a3a8365..c249a37 100644
--- a/hw/ide/core.c
+++ b/hw/ide/core.c
@@ -591,7 +591,6 @@ static void ide_sector_read_cb(void *opaque, int ret)
     s->nsector -= n;
     /* Allow the guest to read the io_buffer */
     ide_transfer_start(s, s->io_buffer, n * BDRV_SECTOR_SIZE, ide_sector_read);
-    s->io_buffer_offset += 512 * n;
     ide_set_irq(s->bus);
 }
 
@@ -635,11 +634,12 @@ static void ide_sector_read(IDEState *s)
                                  ide_sector_read_cb, s);
 }
 
-static void dma_buf_commit(IDEState *s, uint32_t tx_bytes)
+void dma_buf_commit(IDEState *s, uint32_t tx_bytes)
 {
     if (s->bus->dma->ops->commit_buf) {
         s->bus->dma->ops->commit_buf(s->bus->dma, tx_bytes);
     }
+    s->io_buffer_offset += tx_bytes;
     qemu_sglist_destroy(&s->sg);
 }
 
@@ -842,7 +842,6 @@ static void ide_sector_write_cb(void *opaque, int ret)
         n = s->req_nb_sectors;
     }
     s->nsector -= n;
-    s->io_buffer_offset += 512 * n;
 
     ide_set_sector(s, ide_get_sector(s) + n);
     if (s->nsector == 0) {
diff --git a/hw/ide/internal.h b/hw/ide/internal.h
index 40e1aa4..05e93ff 100644
--- a/hw/ide/internal.h
+++ b/hw/ide/internal.h
@@ -536,6 +536,7 @@ int64_t ide_get_sector(IDEState *s);
 void ide_set_sector(IDEState *s, int64_t sector_num);
 
 void ide_start_dma(IDEState *s, BlockCompletionFunc *cb);
+void dma_buf_commit(IDEState *s, uint32_t tx_bytes);
 void ide_dma_error(IDEState *s);
 void ide_abort_command(IDEState *s);
 
-- 
2.1.0