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04 May 2020 08:16:49 -0700 Date: Mon, 4 May 2020 08:22:54 -0700 From: Jacob Pan To: Jean-Philippe Brucker Subject: Re: [PATCH v6 02/25] iommu/ioasid: Add ioasid references Message-ID: <20200504082254.58fc6365@jacob-builder> In-Reply-To: <20200504143932.GC170104@myrica> References: <20200430143424.2787566-1-jean-philippe@linaro.org> <20200430143424.2787566-3-jean-philippe@linaro.org> <20200430113931.0fbf7a37@jacob-builder> <20200430134842.74e596b8@jacob-builder> <20200504143932.GC170104@myrica> Organization: OTC X-Mailer: Claws Mail 3.13.2 (GTK+ 2.24.30; x86_64-pc-linux-gnu) MIME-Version: 1.0 Cc: devicetree@vger.kernel.org, kevin.tian@intel.com, jgg@ziepe.ca, linux-pci@vger.kernel.org, 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, will@kernel.org, christian.koenig@amd.com, linux-arm-kernel@lists.infradead.org X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On Mon, 4 May 2020 16:39:32 +0200 Jean-Philippe Brucker wrote: > On Thu, Apr 30, 2020 at 01:48:42PM -0700, Jacob Pan wrote: > > On Thu, 30 Apr 2020 11:39:31 -0700 > > Jacob Pan wrote: > > > > > > -void ioasid_free(ioasid_t ioasid) > > > > +bool ioasid_free(ioasid_t ioasid) > > > > { > > Sorry I missed this in the last reply. > > > > I think free needs to be unconditional since there is not a good > > way to fail it. > > > > Also can we have more symmetric APIs, seems we don't have > > ioasid_put() in this patchset. > > Yes I was thinking of renaming ioasid_free() to ioasid_put() but got > lazy. > > > How about? > > ioasid_alloc() > > ioasid_free(); //drop reference, mark inactive, but not reclaimed if > > refcount is not zero. > > ioasid_get() // returns err if the ioasid is marked inactive by > > ioasid_free() > > How does the caller know that the ioasid is in active/inactive state, > and not freed/reallocated? > In inactive state, callers of ioasid_find(), ioasid_get() would all fail. Only ioasid_put can still operate on it. In freed state (i.e. not allocated), it will be the same as above with the exception that ioasid_put has no effect. > > ioasid_put();// drop reference, reclaim if refcount is 0. > > I'll add ioasid_put() for now. I'd like to avoid introducing the > inactive state in this patch, Sounds good. I just wanted to consult with you about the above APIs. I will introduce the state when we have a real use. > so shall I change the calls in the > Intel driver to ioasid_put(), and not introduce a new ioasid_free() > for the moment? > Sounds good. > Thanks, > Jean > [Jacob Pan] _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu