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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 12F26C4321B for ; Tue, 11 Jun 2019 09:36:46 +0000 (UTC) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org [140.211.169.12]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id DCD16208E3 for ; Tue, 11 Jun 2019 09:36:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DCD16208E3 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from mail.linux-foundation.org (localhost [127.0.0.1]) by mail.linuxfoundation.org (Postfix) with ESMTP id 89921D9E; Tue, 11 Jun 2019 09:36:45 +0000 (UTC) Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id AD971D89 for ; Tue, 11 Jun 2019 09:36:44 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from huawei.com (szxga04-in.huawei.com [45.249.212.190]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 8113D79 for ; Tue, 11 Jun 2019 09:36:43 +0000 (UTC) Received: from DGGEMS412-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id 7E1052B1E12D93060B1E; Tue, 11 Jun 2019 17:36:40 +0800 (CST) Received: from localhost (10.202.226.61) by DGGEMS412-HUB.china.huawei.com (10.3.19.212) with Microsoft SMTP Server id 14.3.439.0; Tue, 11 Jun 2019 17:36:35 +0800 Date: Tue, 11 Jun 2019 10:36:25 +0100 From: Jonathan Cameron To: Jean-Philippe Brucker Subject: Re: [PATCH 1/8] iommu: Add I/O ASID allocator Message-ID: <20190611103625.00001399@huawei.com> In-Reply-To: <20190610184714.6786-2-jean-philippe.brucker@arm.com> References: <20190610184714.6786-1-jean-philippe.brucker@arm.com> <20190610184714.6786-2-jean-philippe.brucker@arm.com> Organization: Huawei X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; i686-w64-mingw32) MIME-Version: 1.0 X-Originating-IP: [10.202.226.61] X-CFilter-Loop: Reflected Cc: mark.rutland@arm.com, devicetree@vger.kernel.org, will.deacon@arm.com, linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, robh+dt@kernel.org, robin.murphy@arm.com, linux-arm-kernel@lists.infradead.org X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.12 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 Sender: iommu-bounces@lists.linux-foundation.org Errors-To: iommu-bounces@lists.linux-foundation.org On Mon, 10 Jun 2019 19:47:07 +0100 Jean-Philippe Brucker wrote: > Some devices might support multiple DMA address spaces, in particular > those that have the PCI PASID feature. PASID (Process Address Space ID) > allows to share process address spaces with devices (SVA), partition a > device into VM-assignable entities (VFIO mdev) or simply provide > multiple DMA address space to kernel drivers. Add a global PASID > allocator usable by different drivers at the same time. Name it I/O ASID > to avoid confusion with ASIDs allocated by arch code, which are usually > a separate ID space. > > The IOASID space is global. Each device can have its own PASID space, > but by convention the IOMMU ended up having a global PASID space, so > that with SVA, each mm_struct is associated to a single PASID. > > The allocator is primarily used by IOMMU subsystem but in rare occasions > drivers would like to allocate PASIDs for devices that aren't managed by > an IOMMU, using the same ID space as IOMMU. > > Signed-off-by: Jean-Philippe Brucker > Signed-off-by: Jacob Pan Hi, A few trivial comments inline. May be more because I'm not that familiar with xa_array than anything else. Jonathan > --- > The most recent discussion on this patch was at: > https://lkml.kernel.org/lkml/1556922737-76313-4-git-send-email-jacob.jun.pan@linux.intel.com/ > I fixed it up a bit following comments in that series, and removed the > definitions for the custom allocator for now. > > There also is a new version that includes the custom allocator into this > patch, but is currently missing the RCU fixes, at: > https://lore.kernel.org/lkml/1560087862-57608-13-git-send-email-jacob.jun.pan@linux.intel.com/ > --- ... > + > +/** > + * ioasid_alloc - Allocate an IOASID > + * @set: the IOASID set > + * @min: the minimum ID (inclusive) > + * @max: the maximum ID (inclusive) > + * @private: data private to the caller > + * > + * Allocate an ID between @min and @max. The @private pointer is stored > + * internally and can be retrieved with ioasid_find(). > + * > + * Return: the allocated ID on success, or %INVALID_IOASID on failure. > + */ > +ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min, ioasid_t max, > + void *private) > +{ > + u32 id = INVALID_IOASID; > + struct ioasid_data *data; > + > + data = kzalloc(sizeof(*data), GFP_KERNEL); > + if (!data) > + return INVALID_IOASID; > + > + data->set = set; > + data->private = private; > + > + if (xa_alloc(&ioasid_xa, &id, data, XA_LIMIT(min, max), GFP_KERNEL)) { > + pr_err("Failed to alloc ioasid from %d to %d\n", min, max); > + goto exit_free; > + } > + data->id = id; > + > +exit_free: This error flow is perhaps a little more confusing than it needs to be? My assumption (perhaps wrong) is that we only have an id == INVALID_IOASID if the xa_alloc fails, and that we will always have such an id value if it does (I'm not totally sure this second element is true in __xa_alloc). If I'm missing something perhaps a comment on how else we'd get here. > + if (id == INVALID_IOASID) { > + kfree(data); > + return INVALID_IOASID; > + } > + return id; > +} > +EXPORT_SYMBOL_GPL(ioasid_alloc); > + > +/** > + * ioasid_free - Free an IOASID > + * @ioasid: the ID to remove > + */ > +void ioasid_free(ioasid_t ioasid) > +{ > + struct ioasid_data *ioasid_data; > + > + ioasid_data = xa_erase(&ioasid_xa, ioasid); > + > + kfree_rcu(ioasid_data, rcu); > +} > +EXPORT_SYMBOL_GPL(ioasid_free); > + > +/** > + * ioasid_find - Find IOASID data > + * @set: the IOASID set > + * @ioasid: the IOASID to find > + * @getter: function to call on the found object > + * > + * The optional getter function allows to take a reference to the found object > + * under the rcu lock. The function can also check if the object is still valid: > + * if @getter returns false, then the object is invalid and NULL is returned. > + * > + * If the IOASID has been allocated for this set, return the private pointer > + * passed to ioasid_alloc. Private data can be NULL if not set. Return an error > + * if the IOASID is not found or does not belong to the set. Perhaps should make it clear that @set can be null. > + */ > +void *ioasid_find(struct ioasid_set *set, ioasid_t ioasid, > + bool (*getter)(void *)) > +{ > + void *priv = NULL; Set in all paths, so does need to be set here. > + struct ioasid_data *ioasid_data; > + > + rcu_read_lock(); > + ioasid_data = xa_load(&ioasid_xa, ioasid); > + if (!ioasid_data) { > + priv = ERR_PTR(-ENOENT); > + goto unlock; > + } > + if (set && ioasid_data->set != set) { > + /* data found but does not belong to the set */ > + priv = ERR_PTR(-EACCES); > + goto unlock; > + } > + /* Now IOASID and its set is verified, we can return the private data */ > + priv = rcu_dereference(ioasid_data->private); > + if (getter && !getter(priv)) > + priv = NULL; > +unlock: > + rcu_read_unlock(); > + > + return priv; > +} > +EXPORT_SYMBOL_GPL(ioasid_find); > + > +MODULE_LICENSE("GPL"); ... _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu