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Fri, 20 Nov 2020 08:03:23 -0800 (PST) Date: Fri, 20 Nov 2020 08:03:21 -0800 From: Minchan Kim To: Will Deacon Subject: Re: [PATCH 1/6] arm64: pgtable: Fix pte_accessible() Message-ID: <20201120160321.GB3377168@google.com> References: <20201120143557.6715-1-will@kernel.org> <20201120143557.6715-2-will@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20201120143557.6715-2-will@kernel.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201120_110327_280894_E2C1F33F X-CRM114-Status: GOOD ( 13.00 ) 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, Yu Zhao , Anshuman Khandual , Peter Zijlstra , Catalin Marinas , linux-kernel@vger.kernel.org, stable@vger.kernel.org, linux-mm@kvack.org, 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 02:35:52PM +0000, Will Deacon wrote: > pte_accessible() is used by ptep_clear_flush() to figure out whether TLB > invalidation is necessary when unmapping pages for reclaim. Although our > implementation is correct according to the architecture, returning true > only for valid, young ptes in the absence of racing page-table > modifications, this is in fact flawed due to lazy invalidation of old > ptes in ptep_clear_flush_young() where we elide the expensive DSB > instruction for completing the TLB invalidation. > > Rather than penalise the aging path, adjust pte_accessible() to return > true for any valid pte, even if the access flag is cleared. > > Cc: > Fixes: 76c714be0e5e ("arm64: pgtable: implement pte_accessible()") > Reported-by: Yu Zhao > Signed-off-by: Will Deacon Reviewed-by: Minchan Kim _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel