[v1,1/1] scsi-disk: Block Device Characteristics emulation fix

Message ID 20180711205813.22346-1-danielhb413@gmail.com
State New
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Series
  • [v1,1/1] scsi-disk: Block Device Characteristics emulation fix
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Commit Message

Daniel Henrique Barboza July 11, 2018, 8:58 p.m.
The current BDC VPD page (page 0xb1) is too short. This can be
seen running sg_utils:

$ sg_vpd --page=bdc /dev/sda
Block device characteristics VPD page (SBC):
Block device characteristics VPD page length too short=8

By the SCSI spec, the expected size of the SBC page is 0x40.
There is no telling how the guest will behave with a shorter
message - it can ignore it, or worse, make (wrong)
assumptions.

This patch fixes the emulation by setting the size to 0x40.
This is the output of the previous sg_vpd command after
applying it:

$ sg_vpd --page=bdc /dev/sda -v
    inquiry cdb: 12 01 b1 00 fc 00
Block device characteristics VPD page (SBC):
   [PQual=0  Peripheral device type: disk]
  Medium rotation rate is not reported
  Product type: Not specified
  WABEREQ=0
  WACEREQ=0
  Nominal form factor not reported
  FUAB=0
  VBULS=0

To improve readability, this patch also adds the VBULS value
explictly and add comments on the existing fields we're
setting.

Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
---
 hw/scsi/scsi-disk.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

Comments

Paolo Bonzini July 12, 2018, 2:53 p.m. | #1
On 11/07/2018 22:58, Daniel Henrique Barboza wrote:
> The current BDC VPD page (page 0xb1) is too short. This can be
> seen running sg_utils:
> 
> $ sg_vpd --page=bdc /dev/sda
> Block device characteristics VPD page (SBC):
> Block device characteristics VPD page length too short=8
> 
> By the SCSI spec, the expected size of the SBC page is 0x40.
> There is no telling how the guest will behave with a shorter
> message - it can ignore it, or worse, make (wrong)
> assumptions.
> 
> This patch fixes the emulation by setting the size to 0x40.
> This is the output of the previous sg_vpd command after
> applying it:
> 
> $ sg_vpd --page=bdc /dev/sda -v
>     inquiry cdb: 12 01 b1 00 fc 00
> Block device characteristics VPD page (SBC):
>    [PQual=0  Peripheral device type: disk]
>   Medium rotation rate is not reported
>   Product type: Not specified
>   WABEREQ=0
>   WACEREQ=0
>   Nominal form factor not reported
>   FUAB=0
>   VBULS=0
> 
> To improve readability, this patch also adds the VBULS value
> explictly and add comments on the existing fields we're
> setting.
> 
> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>

Kevin kindly agreed to take this through the block tree, so

Acked-by: Paolo Bonzini <pbonzini@redhat.com>

Thanks,

Paolo

> ---
>  hw/scsi/scsi-disk.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c
> index 32f3f96ff8..5ae7baa082 100644
> --- a/hw/scsi/scsi-disk.c
> +++ b/hw/scsi/scsi-disk.c
> @@ -775,11 +775,12 @@ int scsi_disk_emulate_vpd_page(SCSIRequest *req, uint8_t *outbuf)
>      }
>      case 0xb1: /* block device characteristics */
>      {
> -        buflen = 8;
> +        buflen = 0x40;
>          outbuf[4] = (s->rotation_rate >> 8) & 0xff;
>          outbuf[5] = s->rotation_rate & 0xff;
> -        outbuf[6] = 0;
> -        outbuf[7] = 0;
> +        outbuf[6] = 0; /* PRODUCT TYPE */
> +        outbuf[7] = 0; /* WABEREQ | WACEREQ | NOMINAL FORM FACTOR */
> +        outbuf[8] = 0; /* VBULS */
>          break;
>      }
>      case 0xb2: /* thin provisioning */
>
Kevin Wolf July 12, 2018, 3:04 p.m. | #2
Am 12.07.2018 um 16:53 hat Paolo Bonzini geschrieben:
> On 11/07/2018 22:58, Daniel Henrique Barboza wrote:
> > The current BDC VPD page (page 0xb1) is too short. This can be
> > seen running sg_utils:
> > 
> > $ sg_vpd --page=bdc /dev/sda
> > Block device characteristics VPD page (SBC):
> > Block device characteristics VPD page length too short=8
> > 
> > By the SCSI spec, the expected size of the SBC page is 0x40.
> > There is no telling how the guest will behave with a shorter
> > message - it can ignore it, or worse, make (wrong)
> > assumptions.
> > 
> > This patch fixes the emulation by setting the size to 0x40.
> > This is the output of the previous sg_vpd command after
> > applying it:
> > 
> > $ sg_vpd --page=bdc /dev/sda -v
> >     inquiry cdb: 12 01 b1 00 fc 00
> > Block device characteristics VPD page (SBC):
> >    [PQual=0  Peripheral device type: disk]
> >   Medium rotation rate is not reported
> >   Product type: Not specified
> >   WABEREQ=0
> >   WACEREQ=0
> >   Nominal form factor not reported
> >   FUAB=0
> >   VBULS=0
> > 
> > To improve readability, this patch also adds the VBULS value
> > explictly and add comments on the existing fields we're
> > setting.
> > 
> > Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
> 
> Kevin kindly agreed to take this through the block tree, so
> 
> Acked-by: Paolo Bonzini <pbonzini@redhat.com>

Thanks, applied to the block branch.

Kevin

Patch

diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c
index 32f3f96ff8..5ae7baa082 100644
--- a/hw/scsi/scsi-disk.c
+++ b/hw/scsi/scsi-disk.c
@@ -775,11 +775,12 @@  int scsi_disk_emulate_vpd_page(SCSIRequest *req, uint8_t *outbuf)
     }
     case 0xb1: /* block device characteristics */
     {
-        buflen = 8;
+        buflen = 0x40;
         outbuf[4] = (s->rotation_rate >> 8) & 0xff;
         outbuf[5] = s->rotation_rate & 0xff;
-        outbuf[6] = 0;
-        outbuf[7] = 0;
+        outbuf[6] = 0; /* PRODUCT TYPE */
+        outbuf[7] = 0; /* WABEREQ | WACEREQ | NOMINAL FORM FACTOR */
+        outbuf[8] = 0; /* VBULS */
         break;
     }
     case 0xb2: /* thin provisioning */