The patch titled
Subject: asm-generic/tlb: avoid potential double flush
has been added to the -mm tree. Its filename is
asm-generic-tlb-avoid-potential-double-flush.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/asm-generic-tlb-avoid-potential-double-flush.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/asm-generic-tlb-avoid-potential-double-flush.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Subject: asm-generic/tlb: avoid potential double flush
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@xxxxxxxxxxxxx
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
Reported-by: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/asm-generic/tlb.h | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
--- a/include/asm-generic/tlb.h~asm-generic-tlb-avoid-potential-double-flush
+++ a/include/asm-generic/tlb.h
@@ -402,7 +402,12 @@ tlb_update_vma_flags(struct mmu_gather *
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);
_
Patches currently in -mm which might be from peterz@xxxxxxxxxxxxx are
mm-mmu_gather-invalidate-tlb-correctly-on-batch-allocation-failure-and-flush.patch
asm-generic-tlb-avoid-potential-double-flush.patch
asm-gemeric-tlb-remove-stray-function-declarations.patch
asm-generic-tlb-add-missing-config-symbol.patch
asm-generic-tlb-rename-have_rcu_table_free.patch
asm-generic-tlb-rename-have_mmu_gather_page_size.patch
asm-generic-tlb-rename-have_mmu_gather_no_gather.patch
asm-generic-tlb-provide-mmu_gather_table_free.patch
