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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_2 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 9FB5EC47255 for ; Thu, 30 Apr 2020 18:33:32 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 5828F2074A for ; Thu, 30 Apr 2020 18:33:32 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5828F2074A 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 B4C948E0006; Thu, 30 Apr 2020 14:33:31 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id AFDB38E0001; Thu, 30 Apr 2020 14:33:31 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A13488E0006; Thu, 30 Apr 2020 14:33:31 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0149.hostedemail.com [216.40.44.149]) by kanga.kvack.org (Postfix) with ESMTP id 86EE88E0001 for ; Thu, 30 Apr 2020 14:33:31 -0400 (EDT) Received: from smtpin03.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 3F02E181AEF07 for ; Thu, 30 Apr 2020 18:33:31 +0000 (UTC) X-FDA: 76765369422.03.ant23_58d79e5c65011 X-HE-Tag: ant23_58d79e5c65011 X-Filterd-Recvd-Size: 6247 Received: from mga07.intel.com (mga07.intel.com [134.134.136.100]) by imf47.hostedemail.com (Postfix) with ESMTP for ; Thu, 30 Apr 2020 18:33:30 +0000 (UTC) IronPort-SDR: BhrXEdrR+azankFlRPvRE5Tc5nS8K0zV0ZoJYUzE8Kh1LklFwHUpDbjOfwTRws31EaYxG0h4k1 lNQTmIgwmKrQ== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 Apr 2020 11:33:28 -0700 IronPort-SDR: J48xY2cKJPAK1NVryygQbF/nagAXDIYz1I6SC3AHIW5UHcqfCG66Luu3iM/N/zRymWaoSl5F24 9Hf1OxKC5PKg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,336,1583222400"; d="scan'208";a="433056299" Received: from jacob-builder.jf.intel.com (HELO jacob-builder) ([10.7.199.155]) by orsmga005.jf.intel.com with ESMTP; 30 Apr 2020 11:33:28 -0700 Date: Thu, 30 Apr 2020 11:39:31 -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: <20200430113931.0fbf7a37@jacob-builder> In-Reply-To: <20200430143424.2787566-3-jean-philippe@linaro.org> References: <20200430143424.2787566-1-jean-philippe@linaro.org> <20200430143424.2787566-3-jean-philippe@linaro.org> 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 Thu, 30 Apr 2020 16:34:01 +0200 Jean-Philippe Brucker wrote: > Let IOASID users take references to existing ioasids with > ioasid_get(). ioasid_free() drops a reference and only frees the > ioasid when its reference number is zero. It returns whether the > ioasid was freed. > Looks good to me, I was planning to do the same for VT-d use. Just a couple of points for potential extension. I can rebase on top of this. > Signed-off-by: Jean-Philippe Brucker > --- > include/linux/ioasid.h | 10 ++++++++-- > drivers/iommu/ioasid.c | 30 +++++++++++++++++++++++++++++- > 2 files changed, 37 insertions(+), 3 deletions(-) > > diff --git a/include/linux/ioasid.h b/include/linux/ioasid.h > index 6f000d7a0ddcd..609ba6f15b9e3 100644 > --- a/include/linux/ioasid.h > +++ b/include/linux/ioasid.h > @@ -34,7 +34,8 @@ struct ioasid_allocator_ops { > #if IS_ENABLED(CONFIG_IOASID) > ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min, ioasid_t > max, void *private); > -void ioasid_free(ioasid_t ioasid); > +void ioasid_get(ioasid_t ioasid); > +bool ioasid_free(ioasid_t ioasid); > void *ioasid_find(struct ioasid_set *set, ioasid_t ioasid, > bool (*getter)(void *)); > int ioasid_register_allocator(struct ioasid_allocator_ops > *allocator); @@ -48,10 +49,15 @@ static inline ioasid_t > ioasid_alloc(struct ioasid_set *set, ioasid_t min, return > INVALID_IOASID; } > > -static inline void ioasid_free(ioasid_t ioasid) > +static inline void ioasid_get(ioasid_t ioasid) > { > } > > +static inline bool ioasid_free(ioasid_t ioasid) > +{ > + return false; > +} > + > static inline void *ioasid_find(struct ioasid_set *set, ioasid_t > ioasid, bool (*getter)(void *)) > { > diff --git a/drivers/iommu/ioasid.c b/drivers/iommu/ioasid.c > index 0f8dd377aada3..46511ac53e0c8 100644 > --- a/drivers/iommu/ioasid.c > +++ b/drivers/iommu/ioasid.c > @@ -15,6 +15,7 @@ struct ioasid_data { > struct ioasid_set *set; > void *private; > struct rcu_head rcu; > + refcount_t refs; > }; > > /* > @@ -314,6 +315,7 @@ ioasid_t ioasid_alloc(struct ioasid_set *set, > ioasid_t min, ioasid_t max, > data->set = set; > data->private = private; > + refcount_set(&data->refs, 1); > > /* > * Custom allocator needs allocator data to perform platform > specific @@ -345,12 +347,33 @@ ioasid_t ioasid_alloc(struct > ioasid_set *set, ioasid_t min, ioasid_t max, } > EXPORT_SYMBOL_GPL(ioasid_alloc); > > +/** > + * ioasid_get - obtain a reference to the IOASID > + */ > +void ioasid_get(ioasid_t ioasid) why void? what if the ioasid is not valid. > +{ > + 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]