Re: [Qemu-devel] [PATCH v4 0/7] tcg/ppc: Add vector opcodes

[Mark Cave-Ayland]

On 19/06/2019 06:07, Mark Cave-Ayland wrote:

> On 18/06/2019 06:00, Richard Henderson wrote:
> 
>> Ping.  Otherwise I'll include it in my next tcg pull.
>>
>> r~
> 
> I can give this another spin on my test images on a G4 over the next few 
> days. I've
> also added Howard on CC as he reported some issues with the previous 
> iteration at
> https://lists.gnu.org/archive/html/qemu-devel/2019-03/msg06561.html.

I've just given your tcg-ppc-vsx branch a spin here, and like Howard I'm getting
segfaults trying to launch my MacOS images :(  The segfault is weird: it 
doesn't get
caught by an attached gdb and the qemu-system-ppc process seems to hang around 
like a
zombie which makes me think that it's probably an illegal instruction of some 
kind,
but the PPC kernel can't handle it as well as x86 does.

With a bit more work I bisected it down to the first commit in the patchset
(d8dcbb57e9: "tcg/ppc: Initial backend support for Altivec") and then as an
experiment I hacked tcg_can_emit_vec_op() to always return 0 to see if that 
made a
difference, but the segfault still appears.

The commit message mentions that the load and store helpers are also improved, 
so I
wonder if they are what is causing the error rather than the vector parts? Also 
in
the kernel log I see the following messages appearing:

[3639669.374942] qemu-system-ppc[28591]: segfault (11) at 64b8 nip f87280 lr 
f8723c
code 1 in qemu-system-ppc[94e000+aa0000]
[3639669.380015] qemu-system-ppc[28591]: code: 93c10038 91810020 90010044 
7fc802a6
3fde0059 2e030000 3bde6c18 7c9d2378
[3639669.385056] qemu-system-ppc[28591]: code: 813e80a0 7cbb2b78 7cda3378 
7cf93b78
<81428ff8> 9141001c 39400000 81290000

Does that help at all? If not let me know if there are any other tests that 
you'd
like me to try to help debug this.


ATB,

Mark.