[Devel] [PATCH vz8] ms/asm-generic/tlb: avoid potential double flush
Konstantin Khorenko
khorenko at virtuozzo.com
Wed Jun 16 15:50:55 MSK 2021
From: Peter Zijlstra <peterz at infradead.org>
Aneesh reported that:
tlb_flush_mmu()
tlb_flush_mmu_tlbonly()
tlb_flush() <-- #1
tlb_flush_mmu_free()
tlb_table_flush()
tlb_table_invalidate()
tlb_flush_mmu_tlbonly()
tlb_flush() <-- #2
does two TLBIs when tlb->fullmm, because __tlb_reset_range() will not
clear tlb->end in that case.
Observe that any caller to __tlb_adjust_range() also sets at least one of
the tlb->freed_tables || tlb->cleared_p* bits, and those are
unconditionally cleared by __tlb_reset_range().
Change the condition for actually issuing TLBI to having one of those bits
set, as opposed to having tlb->end != 0.
Link: http://lkml.kernel.org/r/20200116064531.483522-4-aneesh.kumar@linux.ibm.com
Signed-off-by: Peter Zijlstra (Intel) <peterz at infradead.org>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar at linux.ibm.com>
Reported-by: "Aneesh Kumar K.V" <aneesh.kumar at linux.ibm.com>
Cc: Michael Ellerman <mpe at ellerman.id.au>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
https://jira.sw.ru/browse/PSBM-101300
(cherry picked from ms commit 0758cd8304942292e95a0f750c374533db378b32)
Signed-off-by: Andrey Ryabinin <aryabinin at virtuozzo.com>
(cherry picked from vz7 commit f64be64b0e3d ("asm-generic/tlb: avoid
potential double flush"))
In the scope of https://jira.sw.ru/browse/PSBM-127854
Signed-off-by: Konstantin Khorenko <khorenko at virtuozzo.com>
---
include/asm-generic/tlb.h | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/include/asm-generic/tlb.h b/include/asm-generic/tlb.h
index 81db3c11bb11..cdb5b3640784 100644
--- a/include/asm-generic/tlb.h
+++ b/include/asm-generic/tlb.h
@@ -152,7 +152,12 @@ static inline void __tlb_reset_range(struct mmu_gather *tlb)
static inline void tlb_flush_mmu_tlbonly(struct mmu_gather *tlb)
{
- if (!tlb->end)
+ /*
+ * Anything calling __tlb_adjust_range() also sets at least one of
+ * these bits.
+ */
+ if (!(tlb->freed_tables || tlb->cleared_ptes || tlb->cleared_pmds ||
+ tlb->cleared_puds || tlb->cleared_p4ds))
return;
tlb_flush(tlb);
--
2.28.0
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