On Fri, 30 Jun 2023, Michael Tokarev wrote:
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.
If something is called frequently enough any small computaion can add up.
In this case invalidating pages is probably a performance hit already and
hopefully does not happen too often but then it's a good idea not to make
it worse. As this is not something that should or could normally happen
and only checks for programming errors I think it's good idea to only do
it when debugging.
Regards,
BALATON Zoltan
Thanks,
/mjt
Signed-off-by: Mark Cave-Ayland <mark.cave-ayl...@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
