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    SubjectRe: [PATCH 2/2] Drivers: scsi: storvsc: Don't pass ATA_16 command to the host
    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@microsoft.com>
    >> Reviewed-by: Haiyang Zhang<haiyangz@microsoft.com>
    >> ---
    >> 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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