Bug#799480: grub-xen-host: XEN domU crash when PV grub chainloads 32-bit domU grub

[Ian Campbell]

On Sat, 2015-09-19 at 18:49 +0200, Andreas Sundstrom wrote:
> Package: grub-xen-host
> Version: 2.02~beta2-22
> Severity: important
> 
> Dear Maintainer,
> 
> Using 64-bit dom0 and 32-bit domU PV (para-virtualized) grub sometimes
> fail when chainloading the domU's grub. 64-bit domU seem to work 100%
> of the time.

Which grub are you starting with from dom0?

If you want to boot a 32-bit guest (which includes chainloading a 32
-bit grub) then you must start with the 32-bit grub-i386-xen.bin grub
binary to create a 32-bit guest.

kexecing from 64-bit to 32-bit is not possible in the general case. In
fact I thought it was _impossible_ in all cases and would have ruled it
out as something you might be doing, except some of these registers
look like 64-bit values:

> (XEN) rax: 0000000000000000   rbx: 0000000000000000   rcx:
0000000000000000
> (XEN) rdx: 0000000000000000   rsi: 0000000000499000   rdi: 0000000000800000
> (XEN) rbp: 000000000000000a   rsp: 00000000005a5ff0   r8:  0000000000000000
> (XEN) r9:  0000000000000000   r10: ffff83023e9b9000   r11: ffff83023e9b9000
> (XEN) r12: 0000033f3d335bfb   r13: ffff82d080300800   r14: ffff82d0802ea940
> (XEN) r15: ffff83005e819000   cr0: 000000008005003b   cr4: 00000000000506f0
> (XEN) cr3: 0000000200b7a000   cr2: 0000000000000000

Ian.