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04 May 2020 13:41:18 -0700 Date: Mon, 4 May 2020 13:47:23 -0700 From: Jacob Pan To: Jean-Philippe Brucker Subject: Re: [PATCH v6 17/25] iommu/arm-smmu-v3: Implement iommu_sva_bind/unbind() Message-ID: <20200504134723.54e2ebcd@jacob-builder> In-Reply-To: <20200504164351.GJ170104@myrica> References: <20200430143424.2787566-1-jean-philippe@linaro.org> <20200430143424.2787566-18-jean-philippe@linaro.org> <20200430141617.6ad4be4c@jacob-builder> <20200504164351.GJ170104@myrica> Organization: OTC X-Mailer: Claws Mail 3.13.2 (GTK+ 2.24.30; x86_64-pc-linux-gnu) MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200504_134124_635183_A3CB1726 X-CRM114-Status: GOOD ( 19.95 ) 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: devicetree@vger.kernel.org, kevin.tian@intel.com, jacob.jun.pan@linux.intel.com, jgg@ziepe.ca, linux-pci@vger.kernel.org, joro@8bytes.org, Jonathan.Cameron@huawei.com, robin.murphy@arm.com, fenghua.yu@intel.com, hch@infradead.org, linux-mm@kvack.org, iommu@lists.linux-foundation.org, zhangfei.gao@linaro.org, catalin.marinas@arm.com, felix.kuehling@amd.com, xuzaibo@huawei.com, will@kernel.org, christian.koenig@amd.com, linux-arm-kernel@lists.infradead.org, baolu.lu@linux.intel.com 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 On Mon, 4 May 2020 18:43:51 +0200 Jean-Philippe Brucker wrote: > On Thu, Apr 30, 2020 at 02:16:17PM -0700, Jacob Pan wrote: > > > +static void arm_smmu_mm_invalidate_range(struct mmu_notifier *mn, > > > + struct mm_struct *mm, > > > + unsigned long start, > > > unsigned long end) +{ > > > + /* TODO: invalidate ATS */ > > > +} > > > + > > > +static void arm_smmu_mm_release(struct mmu_notifier *mn, struct > > > mm_struct *mm) +{ > > > + struct arm_smmu_mmu_notifier *smmu_mn = mn_to_smmu(mn); > > > + struct arm_smmu_domain *smmu_domain; > > > + > > > + mutex_lock(&arm_smmu_sva_lock); > > > + if (smmu_mn->cleared) { > > > + mutex_unlock(&arm_smmu_sva_lock); > > > + return; > > > + } > > > + > > > + smmu_domain = smmu_mn->domain; > > > + > > > + /* > > > + * DMA may still be running. Keep the cd valid but > > > disable > > > + * translation, so that new events will still result in > > > stall. > > > + */ > > Does "disable translation" also disable translated requests? > > No it doesn't disable translated requests, it only prevents the SMMU > from accessing the pgd. > OK. same as VT-d. > > I guess > > release is called after tlb invalidate range, so assuming no more > > devTLB left to generate translated request? > > I'm counting on the invalidate below (here a TODO, implemented in next > patch) to drop all devTLB entries. After that invalidate, the device: > * issues a Translation Request, returns with R=W=0 because we disabled > translation (and it isn't present in the SMMU TLB). > * issues a Page Request, returns with InvalidRequest because > mmget_not_zero() fails. > Same flow. Thanks for the explanation. > > > > > + arm_smmu_write_ctx_desc(smmu_domain, mm->pasid, > > > &invalid_cd); + > > > + arm_smmu_tlb_inv_asid(smmu_domain->smmu, > > > smmu_mn->cd->asid); > > > + /* TODO: invalidate ATS */ > > > + > > If mm release is called after tlb invalidate range, is it still > > necessary to invalidate again? > > No, provided all mappings from the address space are unmapped and > invalidated. I'll double check, but in my tests invalidate range > didn't seem to be called for all mappings on mm exit, so I believe we > do need this. > I think it is safe to invalidate again. There was a concern that mm release may delete IOMMU driver from the notification list and miss tlb invalidate range. I had a hard time to confirm that with ftrace while killing a process, many lost events. > Thanks, > Jean > [Jacob Pan] _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel