On 04/25/2018 02:41 PM, Christian Borntraeger wrote: > You load from address 0. > > On 04/25/2018 02:34 PM, Thomas Huth wrote: >> On 25.04.2018 14:18, Christian Borntraeger wrote: >>> >>> On 04/25/2018 11:08 AM, Thomas Huth wrote: >>> >>>> --- a/pc-bios/s390-ccw/netmain.c >>>> +++ b/pc-bios/s390-ccw/netmain.c >>>> @@ -283,6 +283,15 @@ void panic(const char *string) >>>> } >>>> } >>>> >>>> +void write_subsystem_identification(void) >>>> +{ >>>> + uint32_t *schid = (uint32_t *) 184; >>>> + uint32_t *zeroes = (uint32_t *) 188; >>>> + >>>> + *schid = 0; /* We must not set this for virtio-net */ >>>> + *zeroes = 0; >>>> +} >>>> + >>> >>> I think we actually want to have the CCW devno of that network device >>> stored. It has some value to know which CCW device we bootet from, no? >> >> Actually, I tried that first (and it took quite some time to debug it), >> but the Linux kernel then bails out quite early, without any error >> message. The trace looks like this: >> >> 0x0000000007801802: diag %r1,%r1,776 >> 0x0000000007801780: larl %r2,0x7831004 >> 0x0000000007801786: llgf %r1,8 >> 0x000000000780178c: mvc 0(12,%r0),0(%r2) >> 0x0000000007801792: br %r1 >> 0x0000000000000418: bas %r14,512 >> 0x0000000000000200: mvi 163,1 >> 0x0000000000000204: slr %r0,%r0 >> 0x0000000000000206: lhi %r1,2 >> 0x000000000000020a: sigp %r1,%r0,18 >> 0x000000000000020e: bras %r13,0x252 >> 0x0000000000000252: lmh %r0,%r15,0(%r13) >> 0x0000000000000258: sam31 >> 0x000000000000025a: br %r14 >> 0x000000000000041c: lh %r1,184 >> 0x0000000000000420: bct %r1,1322 >> 0x0000000000000424: l %r1,184 >> 0x0000000000000428: la %r2,1840 >> 0x000000000000042c: bas %r14,640 >> 0x0000000000000280: la %r4,0(%r14) >> 0x0000000000000284: la %r3,792 >> 0x0000000000000288: la %r5,804 >> 0x000000000000028c: la %r6,888 >> 0x0000000000000290: la %r7,20 >> 0x0000000000000294: st %r2,4(%r6) >> 0x0000000000000298: la %r2,80(%r2) >> 0x000000000000029c: la %r6,8(%r6) >> 0x00000000000002a0: bct %r7,660 >> 0x00000000000002a4: lctl %c6,%c6,868 >> 0x00000000000002a8: slr %r2,%r2 >> 0x00000000000002aa: ssch 0(%r3) >> 0x00000000000002ae: bne 786 >> 0x0000000000000312: lpsw 880 >> Guest crashed on cpu 0: disabled-wait >> PSW: 0x000a000000000000 0x0000000000000000 >> >> That's the Lloader function in arch/s390/kernel/head.S which is failing >> here, so seems like Linux tries to load from a block device in case >> there is a value in 184. Thus I assume that 184 has to contain 0 in this >> case. > > Hmm, I think this is because we jump to 418 for your kernel (which is the > loader > that tries to bootstrap the ccw ipl). When you look at ipl.c we override that > and jump to 0x10000 instead for linux (which is also hackish) for image files. > So I guess if we would do a psw restart instead (like you do) on a kernel > image > the normal ipl would also fail.... >
FWIW, zipl also loads linux kernels from 0x10000 $ git grep 0x10000 boot/head.S:.Lstack: .long 0x10000-160 boot/stage2dump.c: if (prefix < 0x10000) /* if < linux-start addr */ boot/tape0.S:KERNEL_OFF = 0x10000 # kernel start code offset boot/tape0.S:KERNEL_ADDR = 0x10000 # default kernel load addr include/zipl.h:#define DEFAULT_IMAGE_ADDRESS 0x10000LL include/zipl.h:#define MINIMUM_ADDRESS 0x10000LL src/bootmap.c: size += DIV_ROUND_UP(st.st_size - 0x10000, src/job.c: &ipl->image_addr, 0, 0x10000, src/job.c: &ipl->ramdisk_addr, 0, 0, 0x10000); src/job.c: &dump->image_addr, 0, 0x10000, src/job.c: 0, 0, 0x10000); src/job.c: &ipl_tape->image_addr, 0, 0x10000, src/job.c: 0, 0, 0x10000);