Re: [Qemu-devel] [PATCH] scsi-bus: fix endianness bug in store_lun()

[Alexey Kardashevskiy]

On 16/03/13 19:13, Paolo Bonzini wrote:
> Il 16/03/2013 08:16, Alexey Kardashevskiy ha scritto:
> > SCSI protocol is defined as big endian. The SCSI command REPORT_LUNS
> > returns the list of LUNs, 8 bytes each.
> >
> > The store_lun() function is called from scsi_target_emulate_report_luns()
> > to fill the LUNs list which is sent later to a guest a response. However
> > it puts the 2 bytes long big-endian value while it is 8 bytes long.
>
> No, LUNs are composed of four 2-byte big-endian values.

I cannot find it in "SCSI Commands References Manual"
(for example here - 
http://www.seagate.com/staticfiles/support/disc/manuals/Interface%20manuals/100293068c.pdf 
). It just says that it is 8 bytes per
LUN and SCSI itself is big endian. Could you please point me to
the correct spec?

> What bug are you trying to fix?

It is a ppc64 system firmware/bios (aka SLOF) which expects 8 bytes big
endian value and therefore cannot boot from SCSI devices with LUN!=0.
I can fix QEMU or SLOF but not sure which one.


> Paolo
>
> > The patch fixes it. Tested on PPC64 platform.
> >
> > Signed-off-by: Alexey Kardashevskiy <address@hidden>
> > ---
> >   hw/scsi-bus.c |    6 +++---
> >   1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/hw/scsi-bus.c b/hw/scsi-bus.c
> > index a97f1cd..7059dc2 100644
> > --- a/hw/scsi-bus.c
> > +++ b/hw/scsi-bus.c
> > @@ -310,11 +310,11 @@ struct SCSITargetReq {
> >   static void store_lun(uint8_t *outbuf, int lun)
> >   {
> >       if (lun < 256) {
> > -        outbuf[1] = lun;
> > +        outbuf[7] = lun;
> >           return;
> >       }
> > -    outbuf[1] = (lun & 255);
> > -    outbuf[0] = (lun >> 8) | 0x40;
> > +    outbuf[7] = (lun & 255);
> > +    outbuf[6] = (lun >> 8) | 0x40;
> >   }
> >
> >   static bool scsi_target_emulate_report_luns(SCSITargetReq *r)


--
Alexey