From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id ADEAFC43331 for ; Thu, 26 Mar 2020 06:46:24 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 73CE2206F8 for ; Thu, 26 Mar 2020 06:46:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="Mn6S3EqL" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 73CE2206F8 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date: Message-ID:From:References:To:Subject:Reply-To:Content-ID:Content-Description :Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=cUJkEQJI+JoWG6Md1M4LRg9jJ2Qvo/UwvsrH6zCyFOk=; b=Mn6S3EqLUsiGoh jKCORyPY2SjyN8DhpgREDafrhC+DDpzNbbp6JKHxGOAjULaCThmZFvnFK1MFqtYS3Wx8jILm80IyT NgYGENW6POOBfHcGuSPPHJQCKi4CCj4MCDIf2xVN5VMnRsQdRbEh2kE5yzxcHPKC2/z9AqNcf5XFh UPPfSOOL2r7Wkc+FTBxQ0UapHenzG+BAa5Qww/hw/VlQKPGWQ93vwz1K46oqZS10V/GK+hxtBGCK2 rRlYXBsdSHWS70c7Oq1OazDQ2sFNAJEVOKmj7700F5wdEkLN+zjUktyaDOvnoGvie6XHmQu05ydQy tiRM1X2M26VA8IsQYUMA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jHMHW-0006l8-FJ; Thu, 26 Mar 2020 06:46:22 +0000 Received: from szxga05-in.huawei.com ([45.249.212.191] helo=huawei.com) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jHMHS-0006jS-Lu for linux-arm-kernel@lists.infradead.org; Thu, 26 Mar 2020 06:46:20 +0000 Received: from DGGEMS414-HUB.china.huawei.com (unknown [172.30.72.58]) by Forcepoint Email with ESMTP id AB80A3012A2B4E7E1AE2; Thu, 26 Mar 2020 14:45:56 +0800 (CST) Received: from [127.0.0.1] (10.173.220.25) by DGGEMS414-HUB.china.huawei.com (10.3.19.214) with Microsoft SMTP Server id 14.3.487.0; Thu, 26 Mar 2020 14:45:48 +0800 Subject: Re: [RFC PATCH v4 0/6] arm64: tlb: add support for TTL feature To: James Morse References: <20200324134534.1570-1-yezhenyu2@huawei.com> From: Zhenyu Ye Message-ID: <7859561b-78b4-4a12-2642-3741d7d3e7b8@huawei.com> Date: Thu, 26 Mar 2020 14:45:46 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.3.0 MIME-Version: 1.0 In-Reply-To: X-Originating-IP: [10.173.220.25] X-CFilter-Loop: Reflected X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200325_234618_891278_6C6E36E4 X-CRM114-Status: GOOD ( 16.15 ) 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: mark.rutland@arm.com, peterz@infradead.org, catalin.marinas@arm.com, linux-mm@kvack.org, guohanjun@huawei.com, will@kernel.org, linux-arch@vger.kernel.org, yuzhao@google.com, maz@kernel.org, steven.price@arm.com, arm@kernel.org, Dave.Martin@arm.com, arnd@arndb.de, suzuki.poulose@arm.com, npiggin@gmail.com, zhangshaokun@hisilicon.com, broonie@kernel.org, rostedt@goodmis.org, prime.zeng@hisilicon.com, tglx@linutronix.de, linux-arm-kernel@lists.infradead.org, xiexiangyou@huawei.com, linux-kernel@vger.kernel.org, aneesh.kumar@linux.ibm.com, akpm@linux-foundation.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi James, On 2020/3/26 0:15, James Morse wrote: > Hi Zhenyu, > > On 3/24/20 1:45 PM, Zhenyu Ye wrote: >> In order to reduce the cost of TLB invalidation, the ARMv8.4 TTL >> feature allows TLBs to be issued with a level allowing for quicker >> invalidation. This series provide support for this feature. >> >> Patch 1 and Patch 2 was provided by Marc on his NV series[1] patches, >> which detect the TTL feature and add __tlbi_level interface. > > How does this interact with THP? > (I don't see anything on that in the series.) > > With THP, there is no one answer to the size of mapping in a VMA. > This is a problem because the arm-arm has in "Translation table level > hints" in D5.10.2 of DDI0487E.a: > | If an incorrect value for the entry being invalidated by the > | instruction is specified in the TTL field, then no entries are > | required by the architecture to be invalidated from the TLB. > > If we get it wrong, not TLB maintenance occurs! > Thanks for your review. With THP, we should update the TTL value after the page collapse and merge. If not sure what it should be, we can set it to 0 to avoid "no TLB maintenance occur" problem. The Table D5-53 in DDI0487E.a says: | when TTL[1:0] is 0b00: | This value is reserved, and hardware should treat this as if TTL[3:2] is 0b00 | when TTL[3:2] is 0b00: | Hardware must assume that the entry can be from any level. > Unless THP leaves its fingerprints on the vma, I think you can only do > this for VMA types that THP can't mess with. (see > transparent_hugepage_enabled()) > I will try to add struct mmu_gather to TLBI interfaces, which has enough info to track tlb's level. See in next patch version! Thanks, Zhenyu . _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel