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Re: [PATCH v2 1/3] icount: preserve cflags when custom tb is about to ex
Re: [PATCH v2 1/3] icount: preserve cflags when custom tb is about to execute
Thu, 11 Nov 2021 12:20:13 +0000
mu4e 1.7.4; emacs 28.0.60
Pavel Dovgalyuk <firstname.lastname@example.org> writes:
> When debugging with the watchpoints, qemu may need to create
> TB with single instruction. This is achieved by setting cpu->cflags_next_tb.
> But when this block is about to execute, it may be interrupted by another
> thread. In this case cflags will be lost and next executed TB will not
> be the special one.
> This patch checks TB exit reason and restores cflags_next_tb to allow
> finding the interrupted block.
> Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgalyuk@ispras.ru>
> accel/tcg/cpu-exec.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
> diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c
> index 2d14d02f6c..df12452b8f 100644
> --- a/accel/tcg/cpu-exec.c
> +++ b/accel/tcg/cpu-exec.c
> @@ -846,6 +846,16 @@ static inline void cpu_loop_exec_tb(CPUState *cpu,
> TranslationBlock *tb,
> * cpu_handle_interrupt. cpu_handle_interrupt will also
> * clear cpu->icount_decr.u16.high.
> + if (cpu->cflags_next_tb == -1
> + && (!use_icount || !(tb->cflags & CF_USE_ICOUNT)
Why check use_icount here? The cflags should always have CF_USE_ICOUNT
set when icount is enabled. Lets not over complicate the inverted ||
tests we have here.
> + || cpu_neg(cpu)->icount_decr.u16.low >= tb->icount))
Is u16.low ever set when icount isn't enabled?
> + /*
> + * icount is disabled or there are enough instructions
> + * in the budget, do not retranslate this block with
> + * different parameters.
> + */
> + cpu->cflags_next_tb = tb->cflags;
> + }
[PATCH v2 2/3] softmmu: fix watchpoint-interrupt races, Pavel Dovgalyuk, 2021/11/11