vioscsi cmd target id

[Rohan Desai]

Having an issue with vioscsi in GCE. vioscsi decrements the target id in
commands it sends to virtio. This means that the upper layers notion of the
target id is off by 1. This is especially problematic when presented a lun
on the last target of a bus. It never gets discovered because the scsipi
probe code sends down an xs with the last target number, which vioscsi then
decrements in the command it sends along. The probe code never moves on to
the next target (since it thinks its probed all the targets on the bus) and
the lun is never discovered. I hit this in GCE for local disks because they
create a new bus with a single target for each local disk.

Here's a patch that fixes the issue for me:

@@ -279,12 +279,12 @@ vioscsi_scsipi_request(struct scsipi_channel *chan,
scsipi_adapter_req_t
goto stuffup;
}
req->lun[0] = 1;
- req->lun[1] = periph->periph_target - 1;
+ req->lun[1] = periph->periph_target;
req->lun[2] = 0x40 | (periph->periph_lun >> 8);
req->lun[3] = periph->periph_lun;
memset(req->lun + 4, 0, 4);
DPRINTF(("%s: command for %u:%u at slot %d\n", __func__,
- periph->periph_target - 1, periph->periph_lun, slot));
+ periph->periph_target, periph->periph_lun, slot));

if ((size_t)xs->cmdlen > sizeof(req->cdb)) {
DPRINTF(("%s: bad cmdlen %zu > %zu\n", __func__,

Any reason for decrementing periph_target in the first place?

[Christos Zoulas]

In article <CAAw6btkQ34JoUNjt-Vht0aKVe=hAVpTwy5K7iD...@mail.gmail.com>,
Rohan Desai <desai....@gmail.com> wrote:
>-=-=-=-=-=-

Yes, somehow the first target presented to me was unusable. I tried it with
qemu..
https://wiki.netbsd.org/tutorials/how_to_setup_virtio_scsi_with_qemu/

christos

[Christos Zoulas]

On Sep 6, 3:04pm, desai....@gmail.com (Rohan Desai) wrote:
-- Subject: Re: vioscsi cmd target id

| Do you mean target 0? Isn't that the virtual bus target? The probing code
| (see scsi_probe_bus in scsiconf.c) should skip this target since it matches
| the channel id set by vioscsi.

Yes... I did not know it was the virtual bus target... Where is it documented?

christos

[Rohan Desai]

Do you mean target 0? Isn't that the virtual bus target? The probing code
(see scsi_probe_bus in scsiconf.c) should skip this target since it matches
the channel id set by vioscsi.

On Thu, Sep 1, 2016 at 10:52 PM, Christos Zoulas <chri...@astron.com>
wrote:

> In article <CAAw6btkQ34JoUNjt-Vht0aKVe=hAVpTwy5K7iDm5ycb6Pza2Ng@mail.

[Rohan Desai]

I don't find it documented anywhere. The chan_id field of struct
scsipi_channel is documented as "adapter's ID for this channel"
(scsipiconf.h). vioscsi.c sets chan_id to 0.

[LYMN]

On Tue, Sep 06, 2016 at 03:04:00PM -0700, Rohan Desai wrote:
> Do you mean target 0? Isn't that the virtual bus target? The probing code
> (see scsi_probe_bus in scsiconf.c) should skip this target since it matches
> the channel id set by vioscsi.
>

On physical scsi controllers the scsi id of the controller is usually 7
because the highest number on the narrow scsi bus wins arbitration (even
for a wide scsi bus this is still the case). Having the controller at 0
is unusual so it has caused some confusion. I guess the smart thing to
do would be to determine the scsi bus controller id somehow and just
skip enumerating that.

--
Brett Lymn
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