Re: [PATCH v2 0/8] target/sparc: Use tcg_gen_lookup_and_goto_ptr

[Richard Henderson <richard.henderson@linaro.org>]

On 6/27/23 11:37, Philippe Mathieu-Daudé wrote:
> On 27/6/23 08:46, Mark Cave-Ayland wrote:
>> On 22/06/2023 13:26, Mark Cave-Ayland wrote:
>>
>>> On 21/06/2023 19:05, Richard Henderson wrote:
>>>
>>>> Changes from v1:
>>>>    * Split into teeny weeny pieces.
>>>>
>>>>    * It turns out the sparc_tr_tb_stop hunk of v1 was buggy,
>>>>      in that things that are not simple branches use DYNAMIC_PC,
>>>>      e.g. the RETT (return from trap) instruction.
>>>>
>>>>      Introduce DYNAMIC_PC_LOOKUP to distinguish the couple of
>>>>      places where we have a dynamic pc, but no other change
>>>>      of state (conditional branches, JMPL, RETURN).
>>>>
>>>>    * Drop the change for WRFPRS, because it's too infrequent.
>>>>      The WRASI change affects memcpy/memset, so that's more important.
>>>>
>>>> Boots Mark's sol8 install cdrom.  :-)
>>>>
>>>> Top of the profile changes from
>>>>
>>>>      41.55%  qemu-system-sparc              [.] cpu_exec_loop
>>>>      14.02%  qemu-system-sparc              [.] cpu_tb_exec
>>>>       8.74%  qemu-system-sparc              [.] tb_lookup
>>>>       2.11%  qemu-system-sparc              [.] tcg_splitwx_to_rw
>>>>       1.63%  memfd:tcg-jit (deleted)        [.] 0x0000000000000004
>>>>
>>>> to
>>>>
>>>>      31.59%  qemu-system-sparc              [.] helper_lookup_tb_ptr
>>>>      17.79%  qemu-system-sparc              [.] tb_lookup
>>>>       5.38%  qemu-system-sparc              [.] compute_all_sub
>>>>       2.38%  qemu-system-sparc              [.] helper_compute_psr
>>>>       2.36%  qemu-system-sparc              [.] helper_check_align
>>>>       1.79%  memfd:tcg-jit (deleted)        [.] 0x000000000063fc8e
>>>>
>>>> This probably indicates that cpu_get_tb_cpu_state could be
>>>> improved to not consume so much overhead.
>>>
>>> Nice! I've just run this through all of my sun4m/sun4u/sun4v test images and I don't 
>>> see any regressions with v2. The guests feel noticeably more responsive too :)
>>>
>>> Tested-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
>>>
>>> I've skimmed the patches and without looking in too much detail they seem to be okay so 
>>> I'm happy to give:
>>>
>>> Acked-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
>>>
>>> Side note: the niagara tests require the patch at 
>>> https://lists.gnu.org/archive/html/qemu-devel/2023-05/msg03537.html which still hasn't 
>>> been merged yet.
>>>
>>>> Richard Henderson (8):
>>>>    target/sparc: Use tcg_gen_lookup_and_goto_ptr in gen_goto_tb
>>>>    target/sparc: Fix npc comparison in sparc_tr_insn_start
>>>>    target/sparc: Drop inline markers from translate.c
>>>>    target/sparc: Introduce DYNAMIC_PC_LOOKUP
>>>>    target/sparc: Use DYNAMIC_PC_LOOKUP for conditional branches
>>>>    target/sparc: Use DYNAMIC_PC_LOOKUP for JMPL
>>>>    target/sparc: Use DYNAMIC_PC_LOOKUP for v9 RETURN
>>>>    target/sparc: Use tcg_gen_lookup_and_goto_ptr for v9 WRASI
>>>>
>>>>   target/sparc/translate.c | 410 ++++++++++++++++++++++-----------------
>>>>   1 file changed, 233 insertions(+), 177 deletions(-)
>>
>> I've just noticed during testing there is an issue with this series when used with a 
>> real SS-5 PROM image (I was using OpenBIOS for my previous tests) which causes it to 
>> assert() almost immediately on startup:
>>
>> $ ./qemu-system-sparc -bios ss5.bin
>> ERROR:../target/sparc/translate.c:5695:sparc_tr_tb_stop: code should not be reached
>> Bail out! ERROR:../target/sparc/translate.c:5695:sparc_tr_tb_stop: code should not be 
>> reached
>> Aborted
> 
> Could you try this fix:
> 
> -- >8 --
> --- a/target/sparc/translate.c
> +++ b/target/sparc/translate.c
> @@ -5682,5 +5682,5 @@ static void sparc_tr_tb_stop(DisasContextBase *dcbase, CPUState *cs)
> 
>           save_npc(dc);
> -        switch (dc->npc) {
> +        switch (dc->npc & 3) {
>           case DYNAMIC_PC_LOOKUP:
>               if (may_lookup) {
> ---
> 
> ?

No, we should have exact equality on those two values.


r~