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Mon, 06 Jul 2020 09:08:07 -0700 (PDT) Date: Mon, 6 Jul 2020 18:07:55 +0200 From: Jean-Philippe Brucker To: Xiang Zheng Cc: iommu@lists.linux-foundation.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, joro@8bytes.org, catalin.marinas@arm.com, will@kernel.org, robin.murphy@arm.com, baolu.lu@linux.intel.com, Jonathan.Cameron@huawei.com, jacob.jun.pan@linux.intel.com, zhangfei.gao@linaro.org, xuzaibo@huawei.com, fenghua.yu@intel.com, hch@infradead.org, Wang Haibin Subject: Re: [PATCH v8 08/12] iommu/arm-smmu-v3: Seize private ASID Message-ID: <20200706160755.GB3214@myrica> References: <20200618155125.1548969-1-jean-philippe@linaro.org> <20200618155125.1548969-9-jean-philippe@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: A55DD1003B760 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 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 Xiang, On Mon, Jul 06, 2020 at 08:40:27PM +0800, Xiang Zheng wrote: > > @@ -1836,7 +1880,20 @@ static struct arm_smmu_ctx_desc *arm_smmu_alloc_shared_cd(struct mm_struct *mm) > > > > arm_smmu_init_cd(cd); > > > > + /* > > + * Serialize against arm_smmu_domain_finalise_s1() and > > + * arm_smmu_domain_free() as we might need to replace the private ASID > > + * from an existing CD. > > + */ > > + mutex_lock(&asid_lock); > > old_cd = arm_smmu_share_asid(asid); > > + if (!old_cd) { > > + ret = xa_insert(&asid_xa, asid, cd, GFP_KERNEL); > > Should we use "xa_store" here? If "asid" has already been used for private, old_cd would be NULL and > the entry indexed by "asid" in the asid_xa remains. Great catch, that's a bug introduced in v7. arm_smmu_share_asid() would allocate a new asid for the private context but does not remove the old entry. For the fix I think it looks clearer if arm_smmu_share_asid() erases the old entry before returning. Thanks, Jean