Re: [Xen-devel] [BUG] XEN domU crash when PV grub chainloads 32-bit domU grub

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 22/01/16 13:08, Vladimir 'φ-coder/phcoder' Serbinenko wrote:
> On 22.01.2016 14:01, Andrew Cooper wrote:
>> On 22/01/16 12:56, Vladimir 'φ-coder/phcoder' Serbinenko wrote:
>>> On 22.09.2015 10:53, Ian Campbell wrote:
>>>> Hi Vladimir & grub-devel,
>>>>
>>>> Do you have any thoughts on this issue with i386 pv-grub2?
>>>>
>>> Is it still an issue? If so I'll try to replicate it. From stack dump I
>>> see that it has jumped to NULL. GRUB has no threads so it's not a race
>>> condition with itself but may be one with some Xen part. An altrnative
>>> possibility is that grub forgets to flush cache at some point in boot
>>> process.
>> Looks like GRUB doesn't have a traptable registered with Xen (the PV
>> equivalent of the IDT).
>>
>> First, Xen tried to inject a #GP fault and found that the entry EIP was
>> at 0 (which is sadly the default if nothing is specified).  It then took
>> a pagefault while attempting to inject the #GP, and crashed the domain.
>>
> Do you have a link how to add one? We can put a catch-stacktrace-abort
> on it.

This is from my microkernel framework, and is probably the most succinct
code implementation:

http://xenbits.xen.org/gitweb/?p=people/andrewcoop/xen-test-framework.git;a=blob;f=arch/x86/pv/traps.c;h=7f9a1908d260659c10f5cbb1d2d234c9fea1edb5;hb=HEAD#l31

The hypercall ABI documentation is:

http://xenbits.xen.org/gitweb/?p=xen.git;a=blob;f=xen/include/public/arch-x86/xen.h;h=cdd93c1c6446a92e89188c6a5132538188825d27;hb=refs/heads/staging#l126

~Andrew