[Qemu-devel] [PATCH 4/7] scsi-disk: introduce dma_readv and dma_writev

[Paolo Bonzini <pbonzini@redhat.com>]

These are replacements for blk_aio_preadv and blk_aio_pwritev that allow
customization of the data path.  They reuse the DMA helpers' DMAIOFunc
callback type, so that the same function can be used in either the
QEMUSGList or the bounce-buffered case.

This customization will be needed in the next patch to do zero-copy
SG_IO on scsi-block.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 hw/scsi/scsi-disk.c | 63 +++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 52 insertions(+), 11 deletions(-)

diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c
index eaadfd6..4b5db59 100644
--- a/hw/scsi/scsi-disk.c
+++ b/hw/scsi/scsi-disk.c
@@ -55,7 +55,21 @@ do { printf("scsi-disk: " fmt , ## __VA_ARGS__); } while (0)
 
 #define TYPE_SCSI_DISK_BASE         "scsi-disk-base"
 
+#define SCSI_DISK_BASE(obj) \
+     OBJECT_CHECK(SCSIDiskState, (obj), TYPE_SCSI_DISK_BASE)
+#define SCSI_DISK_BASE_CLASS(klass) \
+     OBJECT_CLASS_CHECK(SCSIDiskClass, (klass), TYPE_SCSI_DISK_BASE)
+#define SCSI_DISK_BASE_GET_CLASS(obj) \
+     OBJECT_GET_CLASS(SCSIDiskClass, (obj), TYPE_SCSI_DISK_BASE)
+
 typedef struct SCSIDiskState SCSIDiskState;
+typedef struct SCSIDiskClass SCSIDiskClass;
+
+typedef struct SCSIDiskClass {
+    SCSIDeviceClass parent_class;
+    DMAIOFunc       *dma_readv;
+    DMAIOFunc       *dma_writev;
+} SCSIDiskClass;
 
 typedef struct SCSIDiskReq {
     SCSIRequest req;
@@ -317,6 +331,7 @@ done:
 static void scsi_do_read(SCSIDiskReq *r, int ret)
 {
     SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev);
+    SCSIDiskClass *sdc = (SCSIDiskClass *) object_get_class(OBJECT(s));
 
     assert (r->req.aiocb == NULL);
 
@@ -337,16 +352,16 @@ static void scsi_do_read(SCSIDiskReq *r, int ret)
     if (r->req.sg) {
         dma_acct_start(s->qdev.conf.blk, &r->acct, r->req.sg, BLOCK_ACCT_READ);
         r->req.resid -= r->req.sg->size;
-        r->req.aiocb = dma_blk_read(s->qdev.conf.blk, r->req.sg,
-                                    r->sector << BDRV_SECTOR_BITS,
-                                    scsi_dma_complete, r);
+        r->req.aiocb = dma_blk_io(blk_get_aio_context(s->qdev.conf.blk),
+                                  r->req.sg, r->sector << BDRV_SECTOR_BITS,
+                                  sdc->dma_readv, r, scsi_dma_complete, r,
+                                  DMA_DIRECTION_FROM_DEVICE);
     } else {
         scsi_init_iovec(r, SCSI_DMA_BUF_SIZE);
         block_acct_start(blk_get_stats(s->qdev.conf.blk), &r->acct,
                          r->qiov.size, BLOCK_ACCT_READ);
-        r->req.aiocb = blk_aio_preadv(s->qdev.conf.blk,
-                                      r->sector << BDRV_SECTOR_BITS, &r->qiov,
-                                      0, scsi_read_complete, r);
+        r->req.aiocb = sdc->dma_readv(r->sector, &r->qiov,
+                                      scsi_read_complete, r, r);
     }
 
 done:
@@ -506,6 +521,7 @@ static void scsi_write_data(SCSIRequest *req)
 {
     SCSIDiskReq *r = DO_UPCAST(SCSIDiskReq, req, req);
     SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev);
+    SCSIDiskClass *sdc = (SCSIDiskClass *) object_get_class(OBJECT(s));
 
     /* No data transfer may already be in progress */
     assert(r->req.aiocb == NULL);
@@ -542,15 +558,16 @@ static void scsi_write_data(SCSIRequest *req)
     if (r->req.sg) {
         dma_acct_start(s->qdev.conf.blk, &r->acct, r->req.sg, BLOCK_ACCT_WRITE);
         r->req.resid -= r->req.sg->size;
-        r->req.aiocb = dma_blk_write(s->qdev.conf.blk, r->req.sg,
-                                     r->sector << BDRV_SECTOR_BITS,
                                      scsi_dma_complete, r);
+        r->req.aiocb = dma_blk_io(blk_get_aio_context(s->qdev.conf.blk),
+                                  r->req.sg, r->sector << BDRV_SECTOR_BITS,
+                                  sdc->dma_writev, r, scsi_dma_complete, r,
+                                  DMA_DIRECTION_TO_DEVICE);
     } else {
         block_acct_start(blk_get_stats(s->qdev.conf.blk), &r->acct,
                          r->qiov.size, BLOCK_ACCT_WRITE);
-        r->req.aiocb = blk_aio_pwritev(s->qdev.conf.blk,
-                                       r->sector << BDRV_SECTOR_BITS, &r->qiov,
-                                       0, scsi_write_complete, r);
+        r->req.aiocb = sdc->dma_writev(r->sector << BDRV_SECTOR_BITS, &r->qiov,
+                                       scsi_write_complete, r, r);
     }
 }
 
@@ -2658,12 +2675,35 @@ static int scsi_block_parse_cdb(SCSIDevice *d, SCSICommand *cmd,
 
 #endif
 
+static
+BlockAIOCB *scsi_dma_readv(int64_t offset, QEMUIOVector *iov,
+                           BlockCompletionFunc *cb, void *cb_opaque,
+                           void *opaque)
+{
+    SCSIDiskReq *r = opaque;
+    SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev);
+    return blk_aio_preadv(s->qdev.conf.blk, offset, iov, 0, cb, cb_opaque);
+}
+
+static
+BlockAIOCB *scsi_dma_writev(int64_t offset, QEMUIOVector *iov,
+                            BlockCompletionFunc *cb, void *cb_opaque,
+                            void *opaque)
+{
+    SCSIDiskReq *r = opaque;
+    SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev);
+    return blk_aio_pwritev(s->qdev.conf.blk, offset, iov, 0, cb, cb_opaque);
+}
+
 static void scsi_disk_base_class_initfn(ObjectClass *klass, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(klass);
+    SCSIDiskClass *sdc = SCSI_DISK_BASE_CLASS(klass);
 
     dc->fw_name = "disk";
     dc->reset = scsi_disk_reset;
+    sdc->dma_readv = scsi_dma_readv;
+    sdc->dma_writev = scsi_dma_writev;
 }
 
 static const TypeInfo scsi_disk_base_info = {
@@ -2671,6 +2711,7 @@ static const TypeInfo scsi_disk_base_info = {
     .parent        = TYPE_SCSI_DEVICE,
     .class_init    = scsi_disk_base_class_initfn,
     .instance_size = sizeof(SCSIDiskState),
+    .class_size    = sizeof(SCSIDiskClass),
 };
 
 #define DEFINE_SCSI_DISK_PROPERTIES()                                \
-- 
2.5.5