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    SubjectRE: [PATCH RESEND 1/2] Drivers: scsi: storvsc: Set the scsi result correctly when SRB status is INVALID
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    On Mon, 2012-03-19 at 16:50 +0000, KY Srinivasan wrote:
    >
    > > -----Original Message-----
    > > From: James Bottomley [mailto:James.Bottomley@HansenPartnership.com]
    > > Sent: Monday, March 19, 2012 12:13 PM
    > > To: KY Srinivasan
    > > Cc: gregkh@linuxfoundation.org; linux-kernel@vger.kernel.org;
    > > devel@linuxdriverproject.org; ohering@suse.com; hch@infradead.org; linux-
    > > scsi@vger.kernel.org
    > > Subject: Re: [PATCH RESEND 1/2] Drivers: scsi: storvsc: Set the scsi result correctly
    > > when SRB status is INVALID
    > >
    > > On Sun, 2012-03-18 at 17:12 -0700, K. Y. Srinivasan wrote:
    > > > Currently Windows hosts only support a subset of scsi commands and for
    > > commands
    > > > that are not supported, the host returns a generic SRB failure status.
    > > > However, they have agreed to change the return value to indicate that
    > > > the command is not supported. In preparation for that, handle the
    > > > SRB_STATUS_INVALID_REQUEST return value correctly.
    > > >
    > > > I would like to thank Jeff Garzik <jgpobox@gmail.com> and
    > > > Douglas Gilbert <dgilbert@interlog.com> for suggesting the correct approach
    > > > here.
    > > >
    > > > Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
    > > > Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
    > > > ---
    > > > drivers/scsi/storvsc_drv.c | 12 ++++++++++++
    > > > 1 files changed, 12 insertions(+), 0 deletions(-)
    > > >
    > > > diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
    > > > index 44c7a48..018c363 100644
    > > > --- a/drivers/scsi/storvsc_drv.c
    > > > +++ b/drivers/scsi/storvsc_drv.c
    > > > @@ -202,6 +202,7 @@ enum storvsc_request_type {
    > > > #define SRB_STATUS_INVALID_LUN 0x20
    > > > #define SRB_STATUS_SUCCESS 0x01
    > > > #define SRB_STATUS_ERROR 0x04
    > > > +#define SRB_STATUS_INVALID_REQUEST 0x06
    > >
    > > I don't really think this is the correct approach. We already have a
    > > SCSI error return for this, which you're now translating in the driver
    > > and hypervisor. Rather than have a special byte return of
    > > SRB_STATUS_INVALID_REQUEST, why not have the hypervisor do the right
    > > thing and fill in the ILLEGAL_REQUEST sense return. That way you don't
    > > need a special error code and you don't need to construct the sense
    > > buffer in the driver. Now HyperV will be correctly set up for both pass
    > > through and emulated responses. It's surely not much work and you
    > > already process sense data correctly in storvsc_command_completion(), so
    > > you wouldn't need any patches to the driver for this approach.
    >
    > James, the issue here is that currently shipping Windows hosts don't even do
    > what I am handling here.

    Right, I understand that.

    > Based on the input I got from you and Christoph,
    > I convinced the windows team to at least return the SRB status that indicates
    > an illegal request. I will suggest to them that perhaps they should also set the
    > correct sense code and so I would not need this patch.

    Not also; instead of. There's no need for an extra SRB status. Just
    return the standard check condition sense data.

    > However, keep in mind
    > that there is no current ETA on when Windows will ship with these changes - Windows 8
    > may ship with code where they would return an invalid SRB status, but they are not
    > setting the sense code, hence this patch. When the Window host does the "right thing"
    > I will clean this up, but I don't know when that will be.

    I thought you just said you'd only just asked them if they could
    implemented it, in which case no version of windows currently ships with
    this, correct?

    > More importantly, the second patch in this series where I filter out
    > the ATA_16 command
    > on the guest is really important for us. Without that patch on a range
    > on windows hosts
    > including the current beta version of windows8 where the host is
    > returning a generic
    > error in response to ATA_16 command, we cannot boot many Linux
    > distros. If you
    > prefer, I can drop the first patch and re-submit the second patch for
    > consideration now.
    I'm not sure about that either. You presumably translate
    SRB_STATUS_ERROR into DID_TARGET_FAILURE. That should cause the
    termination of the command with prejudice in exactly the same way as an
    ILLEGAL_REQUEST sense code would (minus the useful error information),
    so what's causing the boot failure?

    James




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