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From: Peter Maydell <peter.maydell@linaro.org>
To: qemu-devel@nongnu.org
Subject: [PULL 01/34] target/arm:Set lg_page_size to 0 if either S1 or S2 asks
for it
Date: Thu, 5 Jan 2023 16:43:44 +0000
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In get_phys_addr_twostage() we set the lg_page_size of the result to
the maximum of the stage 1 and stage 2 page sizes. This works for
the case where we do want to create a TLB entry, because we know the
common TLB code only creates entries of the TARGET_PAGE_SIZE and
asking for a size larger than that only means that invalidations
invalidate the whole larger area. However, if lg_page_size is
smaller than TARGET_PAGE_SIZE this effectively means "don't create a
TLB entry"; in this case if either S1 or S2 said "this covers less
than a page and can't go in a TLB" then the final result also should
be marked that way. Set the resulting page size to 0 if either
stage asked for a less-than-a-page entry, and expand the comment
to explain what's going on.
This has no effect for VMSA because currently the VMSA lookup always
returns results that cover at least TARGET_PAGE_SIZE; however when we
add v8R support it will reuse this code path, and for v8R the S1 and
S2 results can be smaller than TARGET_PAGE_SIZE.
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20221212142708.610090-1-peter.maydell@linaro.org
---
target/arm/ptw.c | 16 +++++++++++++---
1 file changed, 13 insertions(+), 3 deletions(-)
diff --git a/target/arm/ptw.c b/target/arm/ptw.c
index f812734bfb2..2e7826dc29b 100644
--- a/target/arm/ptw.c
+++ b/target/arm/ptw.c
@@ -2655,10 +2655,20 @@ static bool get_phys_addr_twostage(CPUARMState *env=
, S1Translate *ptw,
}
=20
/*
- * Use the maximum of the S1 & S2 page size, so that invalidation
- * of pages > TARGET_PAGE_SIZE works correctly.
+ * If either S1 or S2 returned a result smaller than TARGET_PAGE_SIZE,
+ * this means "don't put this in the TLB"; in this case, return a
+ * result with lg_page_size =3D=3D 0 to achieve that. Otherwise,
+ * use the maximum of the S1 & S2 page size, so that invalidation
+ * of pages > TARGET_PAGE_SIZE works correctly. (This works even though
+ * we know the combined result permissions etc only cover the minimum
+ * of the S1 and S2 page size, because we know that the common TLB code
+ * never actually creates TLB entries bigger than TARGET_PAGE_SIZE,
+ * and passing a larger page size value only affects invalidations.)
*/
- if (result->f.lg_page_size < s1_lgpgsz) {
+ if (result->f.lg_page_size < TARGET_PAGE_BITS ||
+ s1_lgpgsz < TARGET_PAGE_BITS) {
+ result->f.lg_page_size =3D 0;
+ } else if (result->f.lg_page_size < s1_lgpgsz) {
result->f.lg_page_size =3D s1_lgpgsz;
}
=20
--=20
2.25.1