[Qemu-devel] [PATCH] scsi-disk: provide "max write same length" for block limits VPD page

[Ming Lei]

Since QEMU claims to support UNMAP, WRITE SAME and WRITE SAME 16
in the LBP VPD page, it is better to provide "max write same length"
in response for block limits VPD page because:

        - T10 SBC-3 doesn't describe priority explicitly when all three
        are enabled
        - host driver may prefer WRITE/WRITE 16, then try to parse
        "max write same length"

Signed-off-by: Ming Lei <address@hidden>
---
 hw/scsi/scsi-disk.c |   14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c
index 2f75d7d..b15bf4f 100644
--- a/hw/scsi/scsi-disk.c
+++ b/hw/scsi/scsi-disk.c
@@ -674,6 +674,20 @@ static int scsi_disk_emulate_inquiry(SCSIRequest *req, 
uint8_t *outbuf)
             outbuf[29] = (unmap_sectors >> 16) & 0xff;
             outbuf[30] = (unmap_sectors >> 8) & 0xff;
             outbuf[31] = unmap_sectors & 0xff;
+
+            /*
+             * maximum write same length, just borrow max unmap
+             * count because write same command need to support
+             * unmap
+             */
+            outbuf[36] = 0;
+            outbuf[37] = 0;
+            outbuf[38] = 0;
+            outbuf[39] = 0;
+            outbuf[40] = (max_unmap_sectors >> 24) & 0xff;
+            outbuf[41] = (max_unmap_sectors >> 16) & 0xff;
+            outbuf[42] = (max_unmap_sectors >> 8) & 0xff;
+            outbuf[43] = max_unmap_sectors & 0xff;
             break;
         }
         case 0xb2: /* thin provisioning */
-- 
1.7.9.5