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); _
