if driver reads data larger than VIRTIO_BLK_F_SIZE_MAX,
it will cause some issue to the DMA engine.

So when upper software wants to read data larger than
VIRTIO_BLK_F_SIZE_MAX, virtio-blk driver split one large
request into multiple smaller ones.

Signed-off-by: Andy Pei <andy.pei@intel.com>
Signed-off-by: Ding Limin <dinglimin@cmss.chinamobile.com>
---
 src/hw/virtio-blk.c | 35 ++++++++++++++++++++++++++++++++++-
 1 file changed, 34 insertions(+), 1 deletion(-)

diff --git a/src/hw/virtio-blk.c b/src/hw/virtio-blk.c
index 82b1d2a..929ba88 100644
--- a/src/hw/virtio-blk.c
+++ b/src/hw/virtio-blk.c
@@ -24,6 +24,11 @@
 #include "virtio-ring.h"
 #include "virtio-blk.h"
 
+#define min(a, b) ({\
+		typeof(a) _a = a;\
+		typeof(b) _b = b;\
+		_a < _b ? _a : _b; })
+
 struct virtiodrive_s {
     struct drive_s drive;
     struct vring_virtqueue *vq;
@@ -82,8 +87,36 @@ virtio_blk_op(struct disk_op_s *op, int write)
             .length     = sizeof(status),
         },
     };
+    u32 max_io_size =
+        vdrive->drive.max_segment_size * vdrive->drive.max_segments;
+    u16 blk_num_max;
+
+    if (vdrive->drive.blksize != 0 && max_io_size != 0)
+        blk_num_max = (u16)max_io_size / vdrive->drive.blksize;
+    else
+        /* default blk_num_max if hardware doesnot advise a proper value */
+        blk_num_max = 8;
 
-    virtio_blk_op_one_segment(vdrive, write, sg);
+    if (op->count <= blk_num_max) {
+        virtio_blk_op_one_segment(vdrive, write, sg);
+    } else {
+        void *p  = op->buf_fl;
+        u16 count = op->count;
+
+        while (count > 0) {
+            u16 blk_num = min(count, blk_num_max);
+            sg[1].length = vdrive->drive.blksize * blk_num;
+            sg[1].addr = p;
+            virtio_blk_op_one_segment(vdrive, write, sg);
+            if (status == VIRTIO_BLK_S_OK) {
+                hdr.sector += blk_num;
+                p += sg[1].length;
+                count -= blk_num;
+            } else {
+                break;
+            }
+        }
+    }
     return status == VIRTIO_BLK_S_OK ? DISK_RET_SUCCESS : DISK_RET_EBADTRACK;
 }
 
-- 
1.8.3.1

_______________________________________________
SeaBIOS mailing list -- seabios@seabios.org
To unsubscribe send an email to seabios-leave@seabios.org

On Tue, Dec 07, 2021 at 09:31:08AM +0800, Andy Pei wrote:
> if driver reads data larger than VIRTIO_BLK_F_SIZE_MAX,
> it will cause some issue to the DMA engine.
> 
> So when upper software wants to read data larger than
> VIRTIO_BLK_F_SIZE_MAX, virtio-blk driver split one large
> request into multiple smaller ones.
> 
> Signed-off-by: Andy Pei <andy.pei@intel.com>
> Signed-off-by: Ding Limin <dinglimin@cmss.chinamobile.com>

Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>

_______________________________________________
SeaBIOS mailing list -- seabios@seabios.org
To unsubscribe send an email to seabios-leave@seabios.org

Hi Gerd,

Thanks for your effort.

-----Original Message-----
From: Gerd Hoffmann <kraxel@redhat.com> 
Sent: Tuesday, December 7, 2021 4:28 PM
To: Pei, Andy <andy.pei@intel.com>
Cc: seabios@seabios.org; kevin@koconnor.net; Ding Limin <dinglimin@cmss.chinamobile.com>
Subject: Re: [PATCH v4 3/3] virtio-blk.: split large IO according to size_max

On Tue, Dec 07, 2021 at 09:31:08AM +0800, Andy Pei wrote:
> if driver reads data larger than VIRTIO_BLK_F_SIZE_MAX, it will cause 
> some issue to the DMA engine.
> 
> So when upper software wants to read data larger than 
> VIRTIO_BLK_F_SIZE_MAX, virtio-blk driver split one large request into 
> multiple smaller ones.
> 
> Signed-off-by: Andy Pei <andy.pei@intel.com>
> Signed-off-by: Ding Limin <dinglimin@cmss.chinamobile.com>

Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>

_______________________________________________
SeaBIOS mailing list -- seabios@seabios.org
To unsubscribe send an email to seabios-leave@seabios.org