Re: [Xen-devel] hvm crash on hypercall event channel

[Daniel Castro <evil.dani@xxxxxxxxx>]

On Tue, Apr 10, 2012 at 9:13 PM, Tim Deegan <tim@xxxxxxx> wrote:
> At 20:30 +0900 on 10 Apr (1334089815), Daniel Castro wrote:
>> Hello All,
>>
>> I am writing the PV-Drivers for Seabios.
>>
>> When I put a request on the front ring and issue the hypercall to
>> notify, the hvm guest crashes.
>>
>> Here is the dmesg output:
>>
>> (XEN) realmode.c:116:d10 Failed to emulate insn.
>> (XEN) realmode.c:166:d10 Real-mode emulation failed @ f000:00001c4b:
>> 0f aa ba b2 00 ec
>
> 0F AA is RSM, which is a pretty surprising instruction to find in a
> hypercall invocation -- or indeed anywhere outside machine-specific SMM
> code.  Is there SMM code in SeaBIOS?  It may be that you've ended up
> jumping to a misaligned instruction boundary.
>
>> Nothing out of the ordinary. Except that the hypercall is issued under
>> 16bit, It works under 32bit.
>
> Are you using the hypercall page to make your hypercall?  Its contents
> don't make sense in 16-bit mode, only in 32-bit and 64-bit.  Since the
> register arguments are 32-bit anyway you might want to make all your
> hypercalls from 32-bit code anyway; otherwise you'll need to make your
> own 16-bit stubs, with the right prefixes for the MOV imm32.

I have no idea how to fix this :(
>
> Cheers,
>
> Tim.



-- 
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| +---------------------------------+ | This space intentionally blank
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| |   | Daniel Castro,                |
| |   | Consultant/Programmer.|
| |   | U Andes                         |
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