On Mon, 25 Jun 2018 10:02:28 +0200
Christian Borntraeger <borntraeger@xxxxxxxxxx> wrote:
> On 06/25/2018 09:27 AM, Christian Borntraeger wrote:
> > Also adding QEMU.
> >
> > On 06/25/2018 09:10 AM, Christian Borntraeger wrote:
> >>
> >>
> >> On 06/22/2018 09:47 PM, Guenter Roeck wrote:
> >>> Hi,
> >>>
> >>> starting with commit 's390/boot: make head.S and als.c be part of the
> >>> decompressor only' in -next, s390 immages no longer boot in qemu.
> >>> As far as I can see, the reason is that the command line is no longer
> >>> passed from qemu to the kernel, which results in a panic because the
> >>> root file system can not be mounted.
> >>>
> >>> Was this change made on purpose ? If so, is there a way to get qemu
> >>> back to working ?
> >>
> >> Certainly not on purpose.
> >>
> >> Vasily, I can reproduce this with KVM and an external kernel boot of the vmlinux file (the elf file)
> >>
> >> e.g.
> >>
> >> qemu-system-s390 -enable-kvm -nographic -kernel vmlinux -append "this string no longer is command line"
> >>
> >> The compressed image (bzImage) seems to work fine though.
> >>
> >> This seems to be an unfortunate side effect of QEMUs ways to "guess" its Linux (checking for start
> >> address 0x10000, which is no longer true for the vmlinux file). With the pure vmlinux elf file
> >> the load address is 0x100000 as there is no unpacker.
> >>
> >> Guenter, can you check if arch/s390/boot/bzImage works for you as a workaround?
> >
> > 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);
> > + }
> >
> > if (ipl->initrd) {
> > ram_addr_t initrd_offset;
> >
> > would put the command line in no matter what the start address is.
>
> Ideally we would do 2 changes:
> - change QEMU to add a commandline to 10480 if specified
> - have a way to fix the kernel elf file to still boot with older QEMUs
>
Agreed on both. Even if we change QEMU now (+ stable), there are many
versions out there that will now fail.
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