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

[Mark Cave-Ayland]

On 22/06/2019 15:20, Mark Cave-Ayland wrote:

> 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.

One more hint: if I try a build of d8dcbb57e9 along with my 
tcg_can_emit_vec_op()
hack and pass --enable-debug-tcg to configure then I get an assert on startup:

qemu-system-ppc: /home/mca/src/qemu/tcg/tcg.c:2207: process_op_defs: Assertion 
`tdefs
!= ((void *)0)' failed.
Aborted


ATB,

Mark.