Re: [PATCH 2/2] accel/tcg: add assert() check in tb_invalidate_phys_page_range__locked()

[Michael Tokarev]

29.06.2023 11:25, Mark Cave-Ayland wrote:
> Add an assert() check in tb_invalidate_phys_page_range__locked() to ensure that
> both the start and last addresses are within the same target page. Note that
> due to performance concerns the check is only enabled when QEMU is configured
> with --enable-debug-tcg.

Performance concerns? That's two ANDs and on compare, - is it really that 
performance
critical?

I'm just asking, I dunno.

Thanks,

/mjt

> Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
> ---
>   accel/tcg/tb-maint.c | 4 ++++
>   1 file changed, 4 insertions(+)
>
> diff --git a/accel/tcg/tb-maint.c b/accel/tcg/tb-maint.c
> index 33ea1aadd1..8cd730dcb0 100644
> --- a/accel/tcg/tb-maint.c
> +++ b/accel/tcg/tb-maint.c
> @@ -1092,6 +1092,10 @@ tb_invalidate_phys_page_range__locked(struct 
> page_collection *pages,
>       TranslationBlock *current_tb = retaddr ? tcg_tb_lookup(retaddr) : NULL;
>   #endif /* TARGET_HAS_PRECISE_SMC */
>   
> +#ifdef CONFIG_DEBUG_TCG
> +    assert((last & TARGET_PAGE_MASK) == (start & TARGET_PAGE_MASK));
> +#endif
> +
>       /*
>        * We remove all the TBs in the range [start, last].
>        * XXX: see if in some cases it could be faster to invalidate all the code