Re: [Qemu-devel] Funny -m arguments can crash

[Avi Kivity <avi@redhat.com>]

On 08/14/2012 01:44 PM, Jan Kiszka wrote:
> On 2012-08-14 12:20, Avi Kivity wrote:
>> On 08/14/2012 11:44 AM, Markus Armbruster wrote:
>>>
>>> Next error:
>>>
>>>     $ gdb --args qemu-system-x86_64 -nodefaults --enable-kvm -vnc :0 -monitor stdio -m 640k
>>>     [...]
>>>     Program received signal SIGSEGV, Segmentation fault.
>>>     [...]
>>>     (gdb) bt
>>>     #0  0x0000003b0de884ac in __memcmp_sse2 () from /lib64/libc.so.6
>>>     #1  0x000000000063f1ad in patch_hypercalls (s=0x139b350)
>>>         at /work/armbru/qemu/hw/i386/../kvmvapic.c:532
>>>     #2  0x000000000063f3fe in vapic_prepare (s=0x139b350)
>>>         at /work/armbru/qemu/hw/i386/../kvmvapic.c:597
>>>     #3  0x000000000063f4ed in vapic_write (opaque=0x139b350, addr=0, data=32, size=
>>>         2) at /work/armbru/qemu/hw/i386/../kvmvapic.c:634
>>>     #4  0x0000000000677a44 in memory_region_write_accessor (opaque=0x139d670, addr=
>>>
>>> Happens when -m argument is a multiple of 4k in [648k..768k].  Only with
>>> --enable-kvm.  With and without my CMOS fix applied.
>> 
>> kvmvapic requires RAM to be present underneath the ROM.  We could fix up
>> kvmvapic to allocate a 4k region and insert it as an overlay, but it's
>> sufficient IMO to require sub-1M users to disable it.  It won't be of
>> any use to the anyway as Windows XP requires more than 1MB.
> 
> We can also easily automatically disable it when there is insufficient
> (<1MB) memory. Will post a patch.

Would be nicer if it auto-disables itself, but don't know if the option
ROM has access to the memory size.


-- 
error compiling committee.c: too many arguments to function