diff mbox series

[PULL,v3,13/20] accel/tcg: Document the faulting lookup in tb_lookup_cmp

Message ID 20220906083815.252478-14-richard.henderson@linaro.org
State Accepted
Commit 9867b30287ec98728e52ed49d03c666e86c90a04
Headers show
Series [PULL,v3,01/20] linux-user/arm: Mark the commpage executable | expand

Commit Message

Richard Henderson Sept. 6, 2022, 8:38 a.m. UTC 
It was non-obvious to me why we can raise an exception in
the middle of a comparison function, but it works.
While nearby, use TARGET_PAGE_ALIGN instead of open-coding.

Acked-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 accel/tcg/cpu-exec.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c
index 7887af6f45..5f43b9769a 100644
--- a/accel/tcg/cpu-exec.c
+++ b/accel/tcg/cpu-exec.c
@@ -198,7 +198,16 @@  static bool tb_lookup_cmp(const void *p, const void *d)
             tb_page_addr_t phys_page2;
             target_ulong virt_page2;
 
-            virt_page2 = (desc->pc & TARGET_PAGE_MASK) + TARGET_PAGE_SIZE;
+            /*
+             * We know that the first page matched, and an otherwise valid TB
+             * encountered an incomplete instruction at the end of that page,
+             * therefore we know that generating a new TB from the current PC
+             * must also require reading from the next page -- even if the
+             * second pages do not match, and therefore the resulting insn
+             * is different for the new TB.  Therefore any exception raised
+             * here by the faulting lookup is not premature.
+             */
+            virt_page2 = TARGET_PAGE_ALIGN(desc->pc);
             phys_page2 = get_page_addr_code(desc->env, virt_page2);
             if (tb->page_addr[1] == phys_page2) {
                 return true;