Re: SCSI regression in 4.11

[James Bottomley <James.Bottomley@HansenPartnership.com>]

On Wed, 2017-03-01 at 10:57 -0800, James Bottomley wrote:
> On Wed, 2017-03-01 at 10:48 -0800, Stephen Hemminger wrote:
> > On Tue, 28 Feb 2017 22:20:58 -0800
> > James Bottomley <jejb@linux.vnet.ibm.com> wrote:
> > 
> > > On Tue, 2017-02-28 at 17:25 -0800, Stephen Hemminger wrote:
> > > > [    1.346023] hv_storvsc:  IO cmd 0x12 0x0 0x0 scsi status 0x0
> > > > srb
> > > > status 0x20 length 36
> > > > [    1.352913] inquiry data: 00000000: 00 aa be f1 5c 98 ff ff
> > > > f0
> > > > 64
> > > > 02 89 ff ff ff ff
> > > > [    1.356543] inquiry data: 00000010: 00 00 00 00 00 00 00 00
> > > > 00
> > > > 00
> > > > 00 00 00 00 00 00
> > > > [    1.359996] inquiry data: 00000020: 00 00 00 00
> > > > [    1.361835] scsi host1: scsi scan: INQUIRY result too short
> > > > (5),
> > > > using 36
> > > > [    1.361888] hv_storvsc:  IO cmd 0xa0 0x0 0x0 scsi status 0x0
> > > > srb
> > > > status 0x1 length 16
> > > > [    1.362307] hv_storvsc:  IO cmd 0x12 0x0 0x0 scsi status 0x0
> > > > srb
> > > > status 0x1 length 36
> > > > [    1.362308] inquiry data: 00000000: 00 23 34 f1 5c 98 ff ff
> > > > f0
> > > > 64
> > > > 02 89 ff ff ff ff
> > > > [    1.362309] inquiry data: 00000010: 00 00 00 00 00 00 00 00
> > > > 00
> > > > 00
> > > > 00 00 00 00 00 00
> > > > [    1.362309] inquiry data: 00000020: 00 00 00 00
> > > > [    1.377423] scsi 1:0:0:1: Direct-Access                     
> > > >   
> > > >     
> > > >          PQ: 0 ANSI: 0  
> > > 
> > > Well, this pinpoints the fault to the block uncopy, I think.  The
> > > Inquiry data is clearly correct in the page frame, so it's not
> > > getting
> > > copied to the scsi_execute() buffer for some reason.
> > > 
> > > James
> > > 
> > 
> > Why do I see different sense data on good (4.10) versus bad (4.11)
> > 
> > Good 4.10 initial INQUIRY buffer
> > [    1.012413] data: 00000000: 00 2e 64 71 db 97 ff ff f0 94 62 96
> > ff
> > ff ff ff
> > [    1.012413] data: 00000010: 00 00 00 00 00 00 00 00 00 00 00 00
> > 00
> > 00 00 00
> > [    1.012414] data: 00000020: 00 00 00 00
> > 
> > Bad 4.11 initial INQUIRY buffer  
> > [    1.218159] data: 00000000: 00 00 05 02 1f 00 00 02 4d 73 66 74
> > 20
> > 20 20 20
> > [    1.225654] data: 00000010: 56 69 72 74 75 61 6c 20 44 69 73 6b
> > 20
> > 20 20 20
> > [    1.242930] data: 00000020: 31 2e 30 20
> > 
> > Is the kmap_atomic looking at the right place?
> 
> Actually, the 4.11 data looks good.  You can tell from the string at
> byte 8.  It's rubbish in the 4.10 one and 'Msft ' in the 4.11 one (I
> assume you just reversed the cut and paste).
> 
> These should be the page physical addresses you sent down to the
> hypervisor, so kmap should work.  Perhaps print out the physical page
> address so we see what we're getting.

Another possible explanation is non zero sg->offset, in which case you
might not see the INQUIRY data because you start at the beginning of
the page.  This shouldn't happen because you specify no alignment
override in the driver, so we should start the INQUIRY buffer on a new
page and copy the data back to the real buffer, but perhaps that's what
changed.

James