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Fri, 27 Apr 2018 09:43:07 -0400 Received: from smtp.codeaurora.org ([198.145.29.96]:55278 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758355AbeD0NnG (ORCPT ); Fri, 27 Apr 2018 09:43:06 -0400 X-Remote-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on pdx-caf-mail.web.codeaurora.org X-Remote-Spam-Level: X-Remote-Spam-Status: No, score=-2.8 required=2.0 tests=ALL_TRUSTED,BAYES_00, DKIM_SIGNED,T_DKIM_INVALID autolearn=no autolearn_force=no version=3.4.0 DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org 2AB146021C Authentication-Results: pdx-caf-mail.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: pdx-caf-mail.web.codeaurora.org; spf=none smtp.mailfrom=cpandya@codeaurora.org Subject: Re: [PATCH v2 2/2] x86/mm: implement free pmd/pte page interfaces To: "joro@8bytes.org" Cc: "guohanjun@huawei.com" , "Hocko, Michal" , "Kani, Toshi" , "wxf.wang@hisilicon.com" , "catalin.marinas@arm.com" , "x86@kernel.org" , "will.deacon@arm.com" , "linux-kernel@vger.kernel.org" , "stable@vger.kernel.org" , "linux-mm@kvack.org" , "mingo@redhat.com" , "willy@infradead.org" , "hpa@zytor.com" , "tglx@linutronix.de" , "bp@suse.de" , "akpm@linux-foundation.org" , "linux-arm-kernel@lists.infradead.org" References: <20180314180155.19492-1-toshi.kani@hpe.com> <20180314180155.19492-3-toshi.kani@hpe.com> <20180426141926.GN15462@8bytes.org> <1524759629.2693.465.camel@hpe.com> <20180426172327.GQ15462@8bytes.org> <1524764948.2693.478.camel@hpe.com> <20180426200737.GS15462@8bytes.org> <1524781764.2693.503.camel@hpe.com> <20180427073719.GT15462@8bytes.org> <5b237058-6617-6af3-8499-8836d95f538d@codeaurora.org> <20180427124828.GW15462@8bytes.org> From: Chintan Pandya Message-ID: Date: Fri, 27 Apr 2018 19:12:57 +0530 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <20180427124828.GW15462@8bytes.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On 4/27/2018 6:18 PM, joro@8bytes.org wrote: > On Fri, Apr 27, 2018 at 05:22:28PM +0530, Chintan Pandya wrote: >> I'm bit confused here. Are you pointing to race within ioremap/vmalloc >> framework while updating the page table or race during tlb ops. Since >> later is arch dependent, I would not comment. But if the race being >> discussed here while altering page tables, I'm not on the same page. > > The race condition is between hardware and software. It is not > sufficient to just remove the software references to the page that is > about to be freed (by clearing the PMD/PUD), also the hardware > references in the page-walk cache need to be removed with a TLB flush. > Otherwise the hardware can use the freed (and possibly reused) page to > establish new TLB entries. Sure ! This is my understanding too (from arm64 context). > > > > Joerg > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > Chintan -- Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project