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Mon, 04 May 2020 09:36:04 -0700 (PDT) Received: from myrica ([2001:171b:226e:c200:c43b:ef78:d083:b355]) by smtp.gmail.com with ESMTPSA id z1sm13717417wmf.15.2020.05.04.09.36.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 04 May 2020 09:36:03 -0700 (PDT) Date: Mon, 4 May 2020 18:35:53 +0200 From: Jean-Philippe Brucker To: Prabhakar Kushwaha Cc: iommu@lists.linux-foundation.org, devicetree@vger.kernel.org, linux-arm-kernel , linux-pci@vger.kernel.org, linux-mm@kvack.org, joro@8bytes.org, Catalin Marinas , Will Deacon , Robin Murphy , 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, Ganapatrao Prabhakerrao Kulkarni , tanmay@marvell.com Subject: Re: [PATCH v6 19/25] iommu/arm-smmu-v3: Add support for Hardware Translation Table Update Message-ID: <20200504163553.GI170104@myrica> References: <20200430143424.2787566-1-jean-philippe@linaro.org> <20200430143424.2787566-20-jean-philippe@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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: Hi, On Mon, May 04, 2020 at 07:54:03PM +0530, Prabhakar Kushwaha wrote: > Dear Jean, > > On Thu, Apr 30, 2020 at 8:11 PM Jean-Philippe Brucker > wrote: > > > > If the SMMU supports it and the kernel was built with HTTU support, enable > > is there any framework/config for HTTU which must be enabled to use this patch? > > > > We can enable HTTU even if CPUs don't support it, because the kernel > > always checks for HW dirty bit and updates the PTE flags atomically. > > > I believe, this statement is valid in context of this patch-set only. > > One cannot use code snipped to test HTTU because exiting > io-pgtable-arm.c driver doesn't have framework to leverage HTTU > benfits. It by-default sets AF=1 and does not set DBM. Right, this patch only sets the hardware access and dirty flags for SVA (page tables shared with the CPU through iommu_bind*()), it doesn't enable anything for iommu_map/unmap(). Although I remember discussing it for VM migration, I don't know of any effort to use hardware access/dirty bits outside of SVA. Thanks, Jean