Re: SSE instruction emulation issues

[Razvan Cojocaru <rcojocaru@bitdefender.com>]

On 07/15/2015 04:55 PM, Fabio Fantoni wrote:
> If you mean to look at the code involved, search the part about the
> problem, think how can go wrong or unexpected, add debug output if
> needed, try quick changes to it ecc... I can do it with simpler software
> and I did something similar with libxl but I don't know how to do the
> same for code like xen/arch/x86/x86_emulate/x86_emulate.c. I already
> took a look at it but I didn't find "MOVAPS" in comments like many others.

MOVAPS emulation is at line 4001 in the x86_emulate.c from staging:

4001     case 0x28: /* {,v}movap{s,d} xmm/m128,xmm */
4002                /* vmovap{s,d} ymm/m256,ymm */

I found this by looking up MOVAPS, getting the opcode (from e.g. here:
http://x86.renejeschke.de/html/file_module_x86_id_180.html) and
searching for 0x28 in the file.

> If so, I suppose that for any change in xen/arch/x86/x86_emulate and
> similar I can't simply make the change, do a make, make install and test
> it immediatly like libxl/xl but I have to rebuild full xen, install it
> and reboot dom0, is it right?

You don't have to do a full rebuild (i.e. make dist), you can just build
the hypervisor (change the current directory to xen/ and just run make
&& make install there, then reboot).

> Can you post a link with a quick reference about x86 emulation and/or
> instruction sets like sse2 which can help me learn what to do or an
> extensive knowledge on the subject is required in this case?

https://docs.oracle.com/cd/E18752_01/html/817-5477/epmpv.html
http://softpixel.com/~cwright/programming/simd/sse2.php


Hope this helps,
Razvan