Re: Regression caught by replay_kernel.py:ReplayKernelNormal.test_aarch64_virt

[Pavel Dovgalyuk <pavel.dovgalyuk@ispras.ru>]

On 27.07.2021 03:39, Cleber Rosa wrote:
> 
> Hi everyone,
> 
> tests/acceptance/replay_kernel.py:ReplayKernelNormal.test_aarch64_virt
> is currently failing consistently (first found that in [1]).
> 
> I've bisected it down to the following commit:

Thanks for bisecting.
I didn't try to understand why the bug happens, but it can be solved 
with the following patch:

--- a/accel/tcg/translate-all.c
+++ b/accel/tcg/translate-all.c
@@ -1428,7 +1428,7 @@ TranslationBlock *tb_gen_code(CPUState *cpu,

      max_insns = cflags & CF_COUNT_MASK;
      if (max_insns == 0) {
-        max_insns = TCG_MAX_INSNS;
+        max_insns = CF_COUNT_MASK;
      }
      QEMU_BUILD_BUG_ON(CF_COUNT_MASK + 1 != TCG_MAX_INSNS);


> 
> ---
> 
> 78ff82bb1b67c0d79113688e4b3427fc99cab9d4 is the first bad commit
> commit 78ff82bb1b67c0d79113688e4b3427fc99cab9d4
> Author: Richard Henderson <richard.henderson@linaro.org>
> 
>      accel/tcg: Reduce CF_COUNT_MASK to match TCG_MAX_INSNS
>      
>      The space reserved for CF_COUNT_MASK was overly large.
>      Reduce to free up cflags bits and eliminate an extra test.
>      
>      Tested-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
>      Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
>      Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
>      Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
>      Message-Id: <20210717221851.2124573-2-richard.henderson@linaro.org>
> 
>   accel/tcg/translate-all.c | 5 ++---
>   include/exec/exec-all.h   | 4 +++-
>   2 files changed, 5 insertions(+), 4 deletions(-)
> 
> ---
> 
> To reproduce it:
> 
> 1. configure --target-list=aarch64-softmmu
> 2. meson compile
> 3. make check-venv
> 4. ./tests/venv/bin/avocado --show=test run tests/acceptance/replay_kernel.py:ReplayKernelNormal.test_aarch64_virt
> 
> PS: I haven't had the time yet to scan the mailing list for possible
> discussions about it.
> 
> [1] https://gitlab.com/qemu-project/qemu/-/jobs/1445513133#L268
>