From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Aneesh Kumar K.V" Subject: [PATCH v2 3/3] asm-generic/tlb: Avoid potential double flush Date: Wed, 18 Dec 2019 11:05:30 +0530 Message-ID: <20191218053530.73053-3-aneesh.kumar@linux.ibm.com> References: <20191218053530.73053-1-aneesh.kumar@linux.ibm.com> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20191218053530.73053-1-aneesh.kumar@linux.ibm.com> Sender: linux-kernel-owner@vger.kernel.org To: akpm@linux-foundation.org, npiggin@gmail.com, mpe@ellerman.id.au, peterz@infradead.org, will@kernel.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-arch@vger.kernel.org, "Aneesh Kumar K.V" List-Id: linux-arch.vger.kernel.org From: Peter Zijlstra 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. Reported-by: "Aneesh Kumar K.V" Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Aneesh Kumar K.V --- 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)) return; tlb_flush(tlb); -- 2.23.0 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:38446 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726674AbfLRFgW (ORCPT ); Wed, 18 Dec 2019 00:36:22 -0500 From: "Aneesh Kumar K.V" Subject: [PATCH v2 3/3] asm-generic/tlb: Avoid potential double flush Date: Wed, 18 Dec 2019 11:05:30 +0530 Message-ID: <20191218053530.73053-3-aneesh.kumar@linux.ibm.com> In-Reply-To: <20191218053530.73053-1-aneesh.kumar@linux.ibm.com> References: <20191218053530.73053-1-aneesh.kumar@linux.ibm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-arch-owner@vger.kernel.org List-ID: To: akpm@linux-foundation.org, npiggin@gmail.com, mpe@ellerman.id.au, peterz@infradead.org, will@kernel.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-arch@vger.kernel.org, "Aneesh Kumar K.V" Message-ID: <20191218053530.aSahknzw_uFEWUN55pCATrAT5s0sWoS7FWAFAILjSn4@z> From: Peter Zijlstra 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. Reported-by: "Aneesh Kumar K.V" Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Aneesh Kumar K.V --- 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)) return; tlb_flush(tlb); -- 2.23.0