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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 98817C4321A for ; Tue, 11 Jun 2019 18:10:28 +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 7862420896 for ; Tue, 11 Jun 2019 18:10:28 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7862420896 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.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 3DED110B0; Tue, 11 Jun 2019 18:10:28 +0000 (UTC) Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 46F7410AF for ; Tue, 11 Jun 2019 18:10:27 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.7.6 Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id 876EF6D6 for ; Tue, 11 Jun 2019 18:10:26 +0000 (UTC) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by fmsmga107.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 11 Jun 2019 11:10:25 -0700 X-ExtLoop1: 1 Received: from jacob-builder.jf.intel.com (HELO jacob-builder) ([10.7.199.155]) by orsmga007.jf.intel.com with ESMTP; 11 Jun 2019 11:10:25 -0700 Date: Tue, 11 Jun 2019 11:13:33 -0700 From: Jacob Pan To: Jean-Philippe Brucker Subject: Re: [PATCH 1/8] iommu: Add I/O ASID allocator Message-ID: <20190611111333.425ce809@jacob-builder> In-Reply-To: <62d1f310-0cba-4d55-0f16-68bba3c64927@arm.com> References: <20190610184714.6786-1-jean-philippe.brucker@arm.com> <20190610184714.6786-2-jean-philippe.brucker@arm.com> <20190611103625.00001399@huawei.com> <62d1f310-0cba-4d55-0f16-68bba3c64927@arm.com> Organization: OTC X-Mailer: Claws Mail 3.13.2 (GTK+ 2.24.30; x86_64-pc-linux-gnu) MIME-Version: 1.0 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 Tue, 11 Jun 2019 15:35:22 +0100 Jean-Philippe Brucker wrote: > On 11/06/2019 10:36, Jonathan Cameron wrote: > >> +/** > >> + * 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. > > Yes we can simplify this: > > return id; > exit_free: > kfree(data) > return INVALID_IOASID; > } > > The XA API doesn't say that @id passed to xa_alloc() won't be modified > in case of error. It's true in the current implementation, but won't > necessarily stay that way. On the other hand I think it's safe to > expect @id to always be set when xa_alloc() succeeds. > the flow with custom allocator is slightly different, but you are right I can simplify it as you suggested. Jonathan, I will add you to the cc list in next version. If you could also review the current version, it would be greatly appreciated. https://lore.kernel.org/lkml/1560087862-57608-13-git-send-email-jacob.jun.pan@linux.intel.com/ > >> +/** > >> + * 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. > > Indeed. But I'm not sure allowing @set to be NULL is such a good idea, > because the data type associated to an ioasid depends on its set. For > example SVA will put an mm_struct in there, and auxiliary domains use > some structure private to the IOMMU domain. > I am not sure we need to count on @set to decipher data type. Whoever does the allocation and owns the IOASID should knows its own data type. My thought was that @set is only used to group IDs, permission check etc. > Jacob, could me make @set mandatory, or do you see a use for a global > search? If @set is NULL, then callers can check if the return pointer > is NULL, but will run into trouble if they try to dereference it. > A global search use case can be for PRQ. IOMMU driver gets a IOASID (first interrupt then retrieve from a queue), it has no idea which @set it belongs to. But the data types are the same for all IOASIDs used by the IOMMU. If @set is NULL, the search does not check set match. It is separate from return pointer. Sorry i am not seeing the problems here. > > > >> + */ > >> +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. > > Right > > Thanks, > Jean [Jacob Pan] _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu