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Re: [PATCH 0/4] target/ppc: Catch invalid real address accesses


From: Mark Cave-Ayland
Subject: Re: [PATCH 0/4] target/ppc: Catch invalid real address accesses
Date: Thu, 29 Jun 2023 09:29:40 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.10.0

On 28/06/2023 08:17, Cédric Le Goater wrote:

qemu-system-ppc.exe -M mac99,via=pmu -cdrom C:\mac-iso\9.2.2.iso -boot d -L 
pc-bios
crashes Mac OS with an address error. (with unpatched and patched builds).

Same on Linux. I get an invalid opcode. QEMU 7.2 work fine though.

C.

That certainly shouldn't happen, and if it worked in 7.2 then there's definitely a regression which has crept in there somewhere. I'll try and bisect this at some point soon, but feel free to try and beat me ;)

bisect points to :

commit e506ad6a05c806bbef460a7d014a184ff8d707a6
Author: Richard Henderson <richard.henderson@linaro.org>
Date:   Mon Mar 6 04:30:11 2023 +0300

     accel/tcg: Pass last not end to tb_invalidate_phys_range
     Pass the address of the last byte to be changed, rather than
     the first address past the last byte.  This avoids overflow
     when the last page of the address space is involved.
     Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
     Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

  include/exec/exec-all.h   |  2 +-
  accel/tcg/tb-maint.c      | 31 ++++++++++++++++---------------
  accel/tcg/translate-all.c |  2 +-
  accel/tcg/user-exec.c     |  2 +-
  softmmu/physmem.c         |  2 +-
  5 files changed, 20 insertions(+), 19 deletions(-)


I think the instruction is fnmadds. Needs more digging.

the invalid opcode is just a symptom of something bad happening.

C.

Indeed, it appears to be a copy/paste error within that commit. I've just posted a proposed fix for this: 20230629082522.606219-1-mark.cave-ayland@ilande.co.uk/T/">https://lore.kernel.org/qemu-devel/20230629082522.606219-1-mark.cave-ayland@ilande.co.uk/T/.

Nick: you may wish to try your series again with this fix applied to see if there are still problems with the CPUs used in the Mac machines.


ATB,

Mark.




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