On 1/16/20 12:15 PM, Aneesh Kumar K.V wrote:
From: Peter Zijlstra <pet...@infradead.org>

Aneesh reported that:

            tlb_flush()                 <-- #1
                  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.

We should possibly get this to stable too along with the first two patches. I am not quiet sure if this will qualify for a stable backport. Hence avoided adding Cc:sta...@kernel.org

Reported-by: "Aneesh Kumar K.V" <aneesh.ku...@linux.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
Signed-off-by: Aneesh Kumar K.V <aneesh.ku...@linux.ibm.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 9e22ac369d1d..b36b3bef5661 100644
--- a/include/asm-generic/tlb.h
+++ b/include/asm-generic/tlb.h
@@ -402,7 +402,12 @@ tlb_update_vma_flags(struct mmu_gather *tlb, struct 
vm_area_struct *vma) { }
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))

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