Re: [Qemu-devel] [qemu-s390x] [PATCH for-2.11] pc-bios/s390-ccw: Fix problem with invalid virtio-scsi LUN when rebooting

[Cornelia Huck <cohuck@redhat.com>]

On Mon, 20 Nov 2017 09:48:36 +0100
Christian Borntraeger <borntraeger@de.ibm.com> wrote:

> Thomas,
> 
> does this patch help as well?
> 
> diff --git a/pc-bios/s390-ccw/Makefile b/pc-bios/s390-ccw/Makefile
> index 6d0c2ee..2687590 100644
> --- a/pc-bios/s390-ccw/Makefile
> +++ b/pc-bios/s390-ccw/Makefile
> @@ -12,7 +12,7 @@ $(call set-vpath, $(SRC_PATH)/pc-bios/s390-ccw)
>  OBJECTS = start.o main.o bootmap.o sclp.o virtio.o virtio-scsi.o virtio-blkdev.o
>  QEMU_CFLAGS := $(filter -W%, $(QEMU_CFLAGS))
>  QEMU_CFLAGS += -ffreestanding -fno-delete-null-pointer-checks -msoft-float
> -QEMU_CFLAGS += -march=z900 -fPIE -fno-strict-aliasing
> +QEMU_CFLAGS += -march=z900 -fPIE -fno-strict-aliasing -fno-zero-initialized-in-bss
>  QEMU_CFLAGS += $(call cc-option, $(QEMU_CFLAGS), -fno-stack-protector)
>  LDFLAGS += -Wl,-pie -nostdlib

If this would actually enable us to kill a whole bird swarm with one
stone, I'd prefer it over the patch below, nicely short though it is.


I plan to pack the one or the other into s390-fixes today and rebuild.

>  
> 
> 
> 
> On 11/17/2017 07:45 PM, Christian Borntraeger wrote:
> > 
> > 
> > On 11/17/2017 07:10 PM, Thomas Huth wrote:  
> >> When rebooting a guest that has a virtio-scsi disk, the s390-ccw
> >> bios sometimes bails out with an error message like this:
> >>
> >> ! SCSI cannot report LUNs: STATUS=02 RSPN=70 KEY=05 CODE=25 QLFR=00, sure !
> >>
> >> Enabling the scsi_req* tracing in QEMU shows that the ccw bios is
> >> trying to execute the REPORT LUNS SCSI command with a LUN != 0, and
> >> this causes the SCSI command to fail.
> >> Looks like we neither clear the BSS of the s390-ccw bios during reboot,
> >> nor do we explicitly set the default_scsi_device.lun value to 0, so
> >> this variable can contain random values from the OS after the reboot.
> >> By setting this variable explicitly to 0, the problem is fixed and
> >> the reboots always succeed.
> >>
> >> Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1514352
> >> Signed-off-by: Thomas Huth <thuth@redhat.com>  
> > 
> > Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
> > 
> > We had these things multile times in the past. The QEMU elf loader does not
> > zero the BSS (it just loads the load section).  Hmm, what about letting the 
> > BIOS zero its bss itself. IIRC the kernel does the same thing. I will have a
> > look into that for 2.12.
> > 
> > PS: Please do not forget to rebuild the bios  
> >> ---
> >>  pc-bios/s390-ccw/virtio-scsi.c | 3 ++-
> >>  1 file changed, 2 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/pc-bios/s390-ccw/virtio-scsi.c b/pc-bios/s390-ccw/virtio-scsi.c
> >> index c92f5d3..4fe4b9d 100644
> >> --- a/pc-bios/s390-ccw/virtio-scsi.c
> >> +++ b/pc-bios/s390-ccw/virtio-scsi.c
> >> @@ -223,7 +223,8 @@ static void virtio_scsi_locate_device(VDev *vdev)
> >>
> >>      for (target = 0; target <= vdev->config.scsi.max_target; target++) {
> >>          sdev->channel = channel;
> >> -        sdev->target = target; /* sdev->lun will be 0 here */
> >> +        sdev->target = target;
> >> +        sdev->lun = 0;          /* LUN has to be 0 for REPORT LUNS */
> >>          if (!scsi_report_luns(vdev, data, sizeof(data))) {
> >>              if (resp.response == VIRTIO_SCSI_S_BAD_TARGET) {
> >>                  continue;
> >>  
> > 
> >   
>