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Re: [Qemu-devel] [PATCH v1 1/1] hw/scsi: Report errors and sense to gues

From: Shinichiro Kawasaki
Subject: Re: [Qemu-devel] [PATCH v1 1/1] hw/scsi: Report errors and sense to guests through scsi-block
Date: Fri, 5 Jul 2019 10:31:36 +0000

On 7/2/19 7:23 PM, Paolo Bonzini wrote:
> On 02/07/19 08:44, Shinichiro Kawasaki wrote:
>> On 7/1/19 8:56 PM, Paolo Bonzini wrote:
>>> On 01/07/19 12:14, Shinichiro Kawasaki wrote:
>>>> I observe four of them listed below in sense data,
>>>> when I ran basic operations to the zoned storage from the guest via 
>>>> scsi-block.
>>>>        21h 04h: UNALIGNED WRITE COMMAND
>>>>        21h 05h: WRITE BOUNDARY VIOLATION
>>>>        21h 06h: ATTEMPT TO READ INVALID DATA
>>>> These ASCs can be reported for write or read commands due to unexpected 
>>>> zone
>>>> status or write pointer status. Reporting these ASCs to the guest, the user
>>>> applications can handle them to manage zone/write pointer status, or help 
>>>> the
>>>> user application developers to understand the failure reason and fix bugs.
>>>> I took a look in scsi_sense_to_errno() and learned that ASCs are grouped in
>>>> errnos. To report the ASCs above to the guest, is it good to add them in 
>>>> group defined in scsi_sense_to_errno()? The ASCs are reported with sense 
>>>> key
>>>> ILLEGAL_REQUEST or DATA_PROTECT, then I think it fits in the function.
>>> The grouping by errno is historical and pretty much broken.  It should
>>> be possible to change it to return just a bool.
>> The errno grouping of scsi_sense_to_errno() is used not only by scsi-disk but
>> also by block/iscsi for error reporting. Can we avoid errno grouping for 
>> iscsi also?
> No, but we can do something like
>      if (scsi_sense_buf_is_guest_recoverable(r->req.sense,
> sizeof(r->req.sense))) {
>          /* These errors are handled by guest. */
>          sdc->update_sense(&r->req);
>          scsi_req_complete(&r->req, *r->status);
>          return true;
>      }
>      error = scsi_sense_buf_to_errno(r->req.sense, sizeof(r->req.sense));
> This way there's generally no need to shoehorn ASC codes into errno.  I
> still have to test my changes, but I hope to send something within a
> couple of days.

Thanks for sharing your thoughts. Now I understand your idea.

I'm awaiting your patch. In case you want me to create the patch based on your 
idea, please let me know. I can afford some time next week to work on it.

Best Regards,
Shin'ichiro Kawasaki

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