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=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 D428CC433E2 for ; Thu, 21 May 2020 14:38:39 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9749220748 for ; Thu, 21 May 2020 14:38:39 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="IOEcaexA" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9749220748 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 061D380008; Thu, 21 May 2020 10:38:39 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 0126880007; Thu, 21 May 2020 10:38:38 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id E42E380008; Thu, 21 May 2020 10:38:38 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0216.hostedemail.com [216.40.44.216]) by kanga.kvack.org (Postfix) with ESMTP id CA15080007 for ; Thu, 21 May 2020 10:38:38 -0400 (EDT) Received: from smtpin03.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 871502C37 for ; Thu, 21 May 2020 14:38:38 +0000 (UTC) X-FDA: 76840982316.03.able68_8599232996142 X-HE-Tag: able68_8599232996142 X-Filterd-Recvd-Size: 4325 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf48.hostedemail.com (Postfix) with ESMTP for ; Thu, 21 May 2020 14:38:37 +0000 (UTC) Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2D32A20671; Thu, 21 May 2020 14:38:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590071917; bh=OiPs36foL9u2qM53WH6N6taB239fXx9YwYNRpOR+uc8=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=IOEcaexAkIOaBlLyjmM4y4cc/lI+AvTt2XG3MJSe97tPOOBgmi21ZXYe/wbygmmAv 5aXAD0JnBq4smiwKKP0tkBFg6mfmBK9KQxomojoIgqFlfdKP3EZ7WzahgMAIQfnPLY ixdP2n51XBJE02yNEqT0nnudoDksFaXfwPwqR4lA= Received: from disco-boy.misterjones.org ([51.254.78.96] helo=www.loen.fr) by disco-boy.misterjones.org with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.92) (envelope-from ) id 1jbmLD-00EFyF-AE; Thu, 21 May 2020 15:38:35 +0100 MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Thu, 21 May 2020 15:38:35 +0100 From: Marc Zyngier To: Will Deacon Cc: Jean-Philippe Brucker , iommu@lists.linux-foundation.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-pci@vger.kernel.org, linux-mm@kvack.org, joro@8bytes.org, catalin.marinas@arm.com, robin.murphy@arm.com, kevin.tian@intel.com, baolu.lu@linux.intel.com, Jonathan.Cameron@huawei.com, jacob.jun.pan@linux.intel.com, christian.koenig@amd.com, felix.kuehling@amd.com, zhangfei.gao@linaro.org, jgg@ziepe.ca, xuzaibo@huawei.com, fenghua.yu@intel.com, hch@infradead.org Subject: Re: [PATCH v7 13/24] iommu/arm-smmu-v3: Enable broadcast TLB maintenance In-Reply-To: <20200521141730.GJ6608@willie-the-truck> References: <20200519175502.2504091-1-jean-philippe@linaro.org> <20200519175502.2504091-14-jean-philippe@linaro.org> <20200521141730.GJ6608@willie-the-truck> User-Agent: Roundcube Webmail/1.4.4 Message-ID: <0c896ad27b43b2de554cf772f9453d0a@kernel.org> X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: will@kernel.org, jean-philippe@linaro.org, iommu@lists.linux-foundation.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-pci@vger.kernel.org, linux-mm@kvack.org, joro@8bytes.org, catalin.marinas@arm.com, robin.murphy@arm.com, kevin.tian@intel.com, baolu.lu@linux.intel.com, Jonathan.Cameron@huawei.com, jacob.jun.pan@linux.intel.com, christian.koenig@amd.com, felix.kuehling@amd.com, zhangfei.gao@linaro.org, jgg@ziepe.ca, xuzaibo@huawei.com, fenghua.yu@intel.com, hch@infradead.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2020-05-21 15:17, Will Deacon wrote: > [+Marc] > > On Tue, May 19, 2020 at 07:54:51PM +0200, Jean-Philippe Brucker wrote: >> The SMMUv3 can handle invalidation targeted at TLB entries with shared >> ASIDs. If the implementation supports broadcast TLB maintenance, >> enable it >> and keep track of it in a feature bit. The SMMU will then be affected >> by >> inner-shareable TLB invalidations from other agents. >> >> A major side-effect of this change is that stage-2 translation >> contexts >> are now affected by all invalidations by VMID. VMIDs are all shared >> and >> the only ways to prevent over-invalidation, since the stage-2 page >> tables >> are not shared between CPU and SMMU, are to either disable BTM or >> allocate >> different VMIDs. This patch does not address the problem. > > This sounds like a potential performance issue, particularly as we > expose > stage-2 contexts via VFIO directly. Maybe we could reserve some portion > of > VMID space for the SMMU? Marc, what do you reckon? Certainly doable when we have 16bits VMIDs. With smaller VMID spaces (like on v8.0), this is a bit more difficult (we do have pretty large v8.0 systems around). How many VMID bits are we talking about? M. -- Jazz is not dead. It just smells funny...