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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 autolearn=no 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 0241EC47254 for ; Mon, 4 May 2020 15:21:02 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id A481B2054F for ; Mon, 4 May 2020 15:21:02 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A481B2054F 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=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 1B33B8E004A; Mon, 4 May 2020 11:21:02 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 163E78E0024; Mon, 4 May 2020 11:21:02 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 054028E004A; Mon, 4 May 2020 11:21:01 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0173.hostedemail.com [216.40.44.173]) by kanga.kvack.org (Postfix) with ESMTP id DF1068E0024 for ; Mon, 4 May 2020 11:21:01 -0400 (EDT) Received: from smtpin14.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 877DF180AD806 for ; Mon, 4 May 2020 15:21:01 +0000 (UTC) X-FDA: 76779399522.14.match40_60295d7831d35 X-HE-Tag: match40_60295d7831d35 X-Filterd-Recvd-Size: 4612 Received: from mga07.intel.com (mga07.intel.com [134.134.136.100]) by imf04.hostedemail.com (Postfix) with ESMTP for ; Mon, 4 May 2020 15:21:00 +0000 (UTC) IronPort-SDR: wrfI54D6IfK+iFiGW3KQymRWXsja4osTdR1wrlwD1tdtGw9f4916GDjxsRCZXn55/wy2k0YKHA mTS/aYd2lMeQ== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 May 2020 08:20:59 -0700 IronPort-SDR: DhyAxpzPRY/Tebzamw5nV/OXd83VAZRNIf4QKSKn9BLW4Q4E1kjVLjHW+nXqmurbxOZK0rot2h utpob8xZoQVQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,352,1583222400"; d="scan'208";a="460700180" Received: from jacob-builder.jf.intel.com (HELO jacob-builder) ([10.7.199.155]) by fmsmga005.fm.intel.com with ESMTP; 04 May 2020 08:20:58 -0700 Date: Mon, 4 May 2020 08:27:03 -0700 From: Jacob Pan To: Jean-Philippe Brucker Cc: iommu@lists.linux-foundation.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-pci@vger.kernel.org, linux-mm@kvack.org, joro@8bytes.org, catalin.marinas@arm.com, will@kernel.org, robin.murphy@arm.com, kevin.tian@intel.com, baolu.lu@linux.intel.com, Jonathan.Cameron@huawei.com, christian.koenig@amd.com, felix.kuehling@amd.com, zhangfei.gao@linaro.org, jgg@ziepe.ca, xuzaibo@huawei.com, fenghua.yu@intel.com, hch@infradead.org, jacob.jun.pan@linux.intel.com Subject: Re: [PATCH v6 02/25] iommu/ioasid: Add ioasid references Message-ID: <20200504082703.2ecc03c1@jacob-builder> In-Reply-To: <20200504142548.GB170104@myrica> References: <20200430143424.2787566-1-jean-philippe@linaro.org> <20200430143424.2787566-3-jean-philippe@linaro.org> <20200430113931.0fbf7a37@jacob-builder> <20200504142548.GB170104@myrica> Organization: OTC X-Mailer: Claws Mail 3.13.2 (GTK+ 2.24.30; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit 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: On Mon, 4 May 2020 16:25:48 +0200 Jean-Philippe Brucker wrote: > On Thu, Apr 30, 2020 at 11:39:31AM -0700, Jacob Pan wrote: > > > +/** > > > + * ioasid_get - obtain a reference to the IOASID > > > + */ > > > +void ioasid_get(ioasid_t ioasid) > > why void? what if the ioasid is not valid. > > My intended use was for the caller to get an additional reference when > they're already holding one. So this should always succeed and I'd > prefer a WARN_ON if the ioasid isn't valid rather than returning an > error. But if you intend to add a state to ioasids between dropping > refcount and free, then a return value makes sense. > Yes, a WARN_ON will do. No need for return value for now. > Thanks, > Jean > > > > > > +{ > > > + struct ioasid_data *ioasid_data; > > > + > > > + spin_lock(&ioasid_allocator_lock); > > > + ioasid_data = xa_load(&active_allocator->xa, ioasid); > > > + if (ioasid_data) > > > + refcount_inc(&ioasid_data->refs); > > > + spin_unlock(&ioasid_allocator_lock); > > > +} > > > +EXPORT_SYMBOL_GPL(ioasid_get); > > > + > > > /** > > > * ioasid_free - Free an IOASID > > > * @ioasid: the ID to remove > > > + * > > > + * Put a reference to the IOASID, free it when the number of > > > references drops to > > > + * zero. > > > + * > > > + * Return: %true if the IOASID was freed, %false otherwise. > > > */ > > > -void ioasid_free(ioasid_t ioasid) > > > +bool ioasid_free(ioasid_t ioasid) > > > { > > > + bool free = false; > > > struct ioasid_data *ioasid_data; > > > > > > spin_lock(&ioasid_allocator_lock); > > > @@ -360,6 +383,10 @@ void ioasid_free(ioasid_t ioasid) > > > goto exit_unlock; > > > } > > > > > > + free = refcount_dec_and_test(&ioasid_data->refs); > > > + if (!free) > > > + goto exit_unlock; > > > + > > Just FYI, we may need to add states for the IOASID, i.g. mark the > > IOASID inactive after free. And prohibit ioasid_get() after freed. > > For VT-d, this is useful when KVM queries the IOASID. > > > > > active_allocator->ops->free(ioasid, > > > active_allocator->ops->pdata); /* Custom allocator needs > > > additional steps to free the xa element */ if > > > (active_allocator->flags & IOASID_ALLOCATOR_CUSTOM) { @@ -369,6 > > > +396,7 @@ void ioasid_free(ioasid_t ioasid) > > > exit_unlock: > > > spin_unlock(&ioasid_allocator_lock); > > > + return free; > > > } > > > EXPORT_SYMBOL_GPL(ioasid_free); > > > > > > > [Jacob Pan] [Jacob Pan]