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[v2,08/17] translate-all: work page-by-page in tb_invalidate_phys_range_1

Message ID 1522980788-1252-9-git-send-email-cota@braap.org
State New
Headers show
Series tcg: tb_lock_removal redux v2 | expand

Commit Message

Emilio Cota April 6, 2018, 2:12 a.m. UTC 
So that we pass a same-page range to tb_invalidate_phys_page_range,
instead of always passing an end address that could be on a different
page.

As discussed with Peter Maydell on the list [1], tb_invalidate_phys_page_range
doesn't actually do much with 'end', which explains why we have never
hit a bug despite going against what the comment on top of
tb_invalidate_phys_page_range requires:

> * Invalidate all TBs which intersect with the target physical address range
> * [start;end[. NOTE: start and end must refer to the *same* physical page.

The appended honours the comment, which avoids confusion.

While at it, rework the loop into a for loop, which is less error prone
(e.g. "continue" won't result in an infinite loop).

[1] https://lists.gnu.org/archive/html/qemu-devel/2017-07/msg09165.html

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Emilio G. Cota <cota@braap.org>
---
 accel/tcg/translate-all.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)
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Patch

diff --git a/accel/tcg/translate-all.c b/accel/tcg/translate-all.c
index 7c72354..b27aacc 100644
--- a/accel/tcg/translate-all.c
+++ b/accel/tcg/translate-all.c
@@ -1378,10 +1378,14 @@  TranslationBlock *tb_gen_code(CPUState *cpu,
  */
 static void tb_invalidate_phys_range_1(tb_page_addr_t start, tb_page_addr_t end)
 {
-    while (start < end) {
-        tb_invalidate_phys_page_range(start, end, 0);
-        start &= TARGET_PAGE_MASK;
-        start += TARGET_PAGE_SIZE;
+    tb_page_addr_t next;
+
+    for (next = (start & TARGET_PAGE_MASK) + TARGET_PAGE_SIZE;
+         start < end;
+         start = next, next += TARGET_PAGE_SIZE) {
+        tb_page_addr_t bound = MIN(next, end);
+
+        tb_invalidate_phys_page_range(start, bound, 0);
     }
 }