linux-kernel - Re: s390 qemu boot failure in -next

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Date:   Tue, 26 Jun 2018 10:29:54 +0200
From:   Cornelia Huck <cohuck@...hat.com>
To:     Christian Borntraeger <borntraeger@...ibm.com>
Cc:     Guenter Roeck <linux@...ck-us.net>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        qemu-s390x <qemu-s390x@...gnu.org>,
        qemu-devel <qemu-devel@...gnu.org>,
        Thomas Huth <thuth@...hat.com>
Subject: Re: s390 qemu boot failure in -next

On Mon, 25 Jun 2018 10:29:46 +0200
Christian Borntraeger <borntraeger@...ibm.com> wrote:

> On 06/25/2018 10:05 AM, Cornelia Huck wrote:
> > On Mon, 25 Jun 2018 09:27:59 +0200
> > Christian Borntraeger <borntraeger@...ibm.com> wrote:

> >> Something like this in QEMU 
> >>
> >> diff --git a/hw/s390x/ipl.c b/hw/s390x/ipl.c
> >> index f278036fa7..14153ce880 100644
> >> --- a/hw/s390x/ipl.c
> >> +++ b/hw/s390x/ipl.c
> >> @@ -187,11 +187,13 @@ static void s390_ipl_realize(DeviceState *dev, Error **errp)
> >>           */
> >>          if (pentry == KERN_IMAGE_START || pentry == 0x800) {
> >>              ipl->start_addr = KERN_IMAGE_START;
> >> -            /* Overwrite parameters in the kernel image, which are "rom" */
> >> -            strcpy(rom_ptr(KERN_PARM_AREA), ipl->cmdline);
> >>          } else {
> >>              ipl->start_addr = pentry;
> >>          }
> >> +       if (ipl->cmdline) {
> >> +            /* If there is a command line, put it in the right place */
> >> +            strcpy(rom_ptr(KERN_PARM_AREA), ipl->cmdline);
> >> +       }  
> > 
> > Check for the magic Linux string (like in the non-elf case) first?  
> 
> Even that does not exists in vmlinux but only in bzImage with the latest patchset
> (in next, but not upstream yet)

Ok.

> >   
> >>  
> >>          if (ipl->initrd) {
> >>              ram_addr_t initrd_offset;
> >>
> >> would put the command line in no matter what the start address is.  
> > 
> > I'm for putting that one in (and backporting it to qemu-stable). It's a
> > bit worrying, though, that our ipl code is so fragile...  
> 
> We actually have to combine this with Thomas fix (to check for rom_ptr returning
> something sane). It seems that ipl->commandline is always there, so we have to
> check for strlen!=0 it seems..
> 
> I mean if somebody ask for "-append something" we can certainly always write something
> if there is rom/ram.

Given that the uncompressed image is not supposed to be bootable
anymore, does it make sense to add this anyway?

I'll go ahead and queue Thomas' fix, though.