Re: [PATCH 2/2] Drivers: scsi: storvsc: Don't pass ATA_16 commandto the host

[Douglas Gilbert]

On 12-03-17 04:04 PM, Jeff Garzik wrote:
> On 03/16/2012 04:24 PM, K. Y. Srinivasan wrote:
> > The current Windows hosts don't handle the ATA_16 command and furthermore
> > return a generic error code after filtering the command on the host side.
> > For now filter the command on the guest side until the host is modified to
> > properly handle unsupported commands.
> >
> > Signed-off-by: K. Y. Srinivasan<kys@xxxxxxxxxxxxx>
> > Reviewed-by: Haiyang Zhang<haiyangz@xxxxxxxxxxxxx>
> > ---
> > drivers/scsi/storvsc_drv.c | 9 +++++++++
> > 1 files changed, 9 insertions(+), 0 deletions(-)
> >
> > diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
> > index 8b967c9..783bab8 100644
> > --- a/drivers/scsi/storvsc_drv.c
> > +++ b/drivers/scsi/storvsc_drv.c
> > @@ -1229,8 +1229,17 @@ static bool storvsc_scsi_cmd_ok(struct scsi_cmnd *scmnd)
> > /*
> > * smartd sends this command and the host does not handle
> > * this. So, don't send it.
> > + * The current Windows hosts implement a subset of scsi commands
> > + * and for the commands that are not implemented, the host filters
> > + * them and returns a generic failure SRB status. I have been in
> > + * discussions with the Windows team to return the appropriate SRB
> > + * status code for unsupported scsi commands and while they have
> > + * agreed to implement this, it is not clear when this change will be
> > + * available. Consequently, filtering the command before submitting it
> > + * to the host is a resonable interim solution.
> > */
> > case SET_WINDOW:
> > + case ATA_16:
> > scmnd->result = ILLEGAL_REQUEST<< 16;
> > allowed = false;
>
> It would be even nicer to fill out a nice SCSI status for this. For an illegal
> request such as this, the libata SCSI simulator (drivers/ata/libata-scsi.c) uses
> a more complete sense buffer setup,
>
> static void ata_scsi_set_sense(struct scsi_cmnd *cmd, u8 sk,
> u8 asc, u8 ascq)
> {
> cmd->result = (DRIVER_SENSE << 24) | SAM_STAT_CHECK_CONDITION;
>
> scsi_build_sense_buffer(0, cmd->sense_buffer, sk, asc, ascq);
> }
>
> and calls this function for invalid/unknown/unsupported command ops thusly,
>
> ata_scsi_set_sense(cmd, ILLEGAL_REQUEST, 0x20, 0x0);
> /* "Invalid command operation code" */
>
> Supplying asc/ascq provides additional information that may be useful in
> determining whether or not to retry, provide better error diagnostics, etc.
>
> The asc/ascq values are found in the SCSI standards documents.

Jeff,
I agree with your suggestion and would point out that the
originally proposed:
    scmnd->result = ILLEGAL_REQUEST<<  16;

is just plain wrong. result[23:16] is a Linux invented host byte
code (they typically start with "DID_") while ILLEGAL_REQUEST is
a SCSI sense key.

Doug Gilbert

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