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Fri, 20 Nov 2020 12:40:09 -0800 (PST) Date: Fri, 20 Nov 2020 13:40:05 -0700 From: Yu Zhao To: Will Deacon Subject: Re: [PATCH 6/6] mm: proc: Avoid fullmm flush for young/dirty bit toggling Message-ID: <20201120204005.GC1303870@google.com> References: <20201120143557.6715-1-will@kernel.org> <20201120143557.6715-7-will@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20201120143557.6715-7-will@kernel.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201120_154012_622492_771FF696 X-CRM114-Status: GOOD ( 20.05 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kernel-team@android.com, Anshuman Khandual , Peter Zijlstra , Catalin Marinas , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Minchan Kim , Linus Torvalds , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Nov 20, 2020 at 02:35:57PM +0000, Will Deacon wrote: > clear_refs_write() uses the 'fullmm' API for invalidating TLBs after > updating the page-tables for the current mm. However, since the mm is not > being freed, this can result in stale TLB entries on architectures which > elide 'fullmm' invalidation. > > Ensure that TLB invalidation is performed after updating soft-dirty > entries via clear_refs_write() by using the non-fullmm API to MMU gather. > > Signed-off-by: Will Deacon > --- > fs/proc/task_mmu.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c > index a76d339b5754..316af047f1aa 100644 > --- a/fs/proc/task_mmu.c > +++ b/fs/proc/task_mmu.c > @@ -1238,7 +1238,7 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf, > count = -EINTR; > goto out_mm; > } > - tlb_gather_mmu_fullmm(&tlb, mm); > + tlb_gather_mmu(&tlb, mm, 0, TASK_SIZE); Let's assume my reply to patch 4 is wrong, and therefore we still need tlb_gather/finish_mmu() here. But then wouldn't this change deprive architectures other than ARM the opportunity to optimize based on the fact it's a full-mm flush? It seems to me ARM's interpretation of tlb->fullmm is a special case, not the other way around. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel