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=-9.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 C5A26C4363D for ; Thu, 24 Sep 2020 18:29:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7264A2311E for ; Thu, 24 Sep 2020 18:29:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728747AbgIXS3q convert rfc822-to-8bit (ORCPT ); Thu, 24 Sep 2020 14:29:46 -0400 Received: from lhrrgout.huawei.com ([185.176.76.210]:2916 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728707AbgIXS3p (ORCPT ); Thu, 24 Sep 2020 14:29:45 -0400 Received: from lhreml721-chm.china.huawei.com (unknown [172.18.7.106]) by Forcepoint Email with ESMTP id F180640490732B561407; Thu, 24 Sep 2020 19:29:43 +0100 (IST) Received: from lhreml710-chm.china.huawei.com (10.201.108.61) by lhreml721-chm.china.huawei.com (10.201.108.72) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1913.5; Thu, 24 Sep 2020 19:29:43 +0100 Received: from lhreml710-chm.china.huawei.com ([169.254.81.184]) by lhreml710-chm.china.huawei.com ([169.254.81.184]) with mapi id 15.01.1913.007; Thu, 24 Sep 2020 19:29:43 +0100 From: Shameerali Kolothum Thodi To: Jacob Pan , "iommu@lists.linux-foundation.org" , LKML , Jean-Philippe Brucker , Lu Baolu , Joerg Roedel , David Woodhouse CC: "Tian, Kevin" , Raj Ashok , "Wu Hao" Subject: RE: [PATCH v2 4/9] iommu/ioasid: Add reference couting functions Thread-Topic: [PATCH v2 4/9] iommu/ioasid: Add reference couting functions Thread-Index: AQHWeFM+3LMH6JurcEu9bAF2eVkkYql4RlcA Date: Thu, 24 Sep 2020 18:29:43 +0000 Message-ID: References: <1598070918-21321-1-git-send-email-jacob.jun.pan@linux.intel.com> <1598070918-21321-5-git-send-email-jacob.jun.pan@linux.intel.com> In-Reply-To: <1598070918-21321-5-git-send-email-jacob.jun.pan@linux.intel.com> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.47.86.144] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Jacob, > -----Original Message----- > From: iommu [mailto:iommu-bounces@lists.linux-foundation.org] On Behalf Of > Jacob Pan > Sent: 22 August 2020 05:35 > To: iommu@lists.linux-foundation.org; LKML ; > Jean-Philippe Brucker ; Lu Baolu > ; Joerg Roedel ; David > Woodhouse > Cc: Tian, Kevin ; Raj Ashok ; Wu > Hao > Subject: [PATCH v2 4/9] iommu/ioasid: Add reference couting functions > > There can be multiple users of an IOASID, each user could have hardware > contexts associated with the IOASID. In order to align lifecycles, > reference counting is introduced in this patch. It is expected that when > an IOASID is being freed, each user will drop a reference only after its > context is cleared. > > Signed-off-by: Jacob Pan > --- > drivers/iommu/ioasid.c | 113 > +++++++++++++++++++++++++++++++++++++++++++++++++ > include/linux/ioasid.h | 4 ++ > 2 files changed, 117 insertions(+) > > diff --git a/drivers/iommu/ioasid.c b/drivers/iommu/ioasid.c > index f73b3dbfc37a..5f31d63c75b1 100644 > --- a/drivers/iommu/ioasid.c > +++ b/drivers/iommu/ioasid.c > @@ -717,6 +717,119 @@ int ioasid_set_for_each_ioasid(struct ioasid_set > *set, > EXPORT_SYMBOL_GPL(ioasid_set_for_each_ioasid); > > /** > + * IOASID refcounting rules > + * - ioasid_alloc() set initial refcount to 1 > + * > + * - ioasid_free() decrement and test refcount. > + * If refcount is 0, ioasid will be freed. Deleted from the system-wide > + * xarray as well as per set xarray. The IOASID will be returned to the > + * pool and available for new allocations. > + * > + * If recount is non-zero, mark IOASID as > IOASID_STATE_FREE_PENDING. > + * No new reference can be added. The IOASID is not returned to the > pool > + * for reuse. > + * After free, ioasid_get() will return error but ioasid_find() and other > + * non refcount adding APIs will continue to work until the last reference > + * is dropped > + * > + * - ioasid_get() get a reference on an active IOASID > + * > + * - ioasid_put() decrement and test refcount of the IOASID. > + * If refcount is 0, ioasid will be freed. Deleted from the system-wide > + * xarray as well as per set xarray. The IOASID will be returned to the > + * pool and available for new allocations. > + * Do nothing if refcount is non-zero. > + * Is it better to have a return for this based on whether ioasid is freed or not? I was going through Jean's SMMUv3 SVA patches[1] and that one returns true if ioasid was freed. And that info is subsequently used to reset the pasid associated with a mm. Though, not sure that is still relevant or not. Thanks, Shameer 1. https://lore.kernel.org/linux-iommu/20200918101852.582559-3-jean-philippe@linaro.org/ > + * - ioasid_find() does not take reference, caller must hold reference > + * > + * ioasid_free() can be called multiple times without error until all refs are > + * dropped. > + */ > + > +int ioasid_get_locked(struct ioasid_set *set, ioasid_t ioasid) > +{ > + struct ioasid_data *data; > + > + data = xa_load(&active_allocator->xa, ioasid); > + if (!data) { > + pr_err("Trying to get unknown IOASID %u\n", ioasid); > + return -EINVAL; > + } > + if (data->state == IOASID_STATE_FREE_PENDING) { > + pr_err("Trying to get IOASID being freed%u\n", ioasid); > + return -EBUSY; > + } > + > + if (set && data->set != set) { > + pr_err("Trying to get IOASID not in set%u\n", ioasid); > + /* data found but does not belong to the set */ > + return -EACCES; > + } > + refcount_inc(&data->users); > + > + return 0; > +} > +EXPORT_SYMBOL_GPL(ioasid_get_locked); > + > +/** > + * ioasid_get - Obtain a reference of an ioasid > + * @set > + * @ioasid > + * > + * Check set ownership if @set is non-null. > + */ > +int ioasid_get(struct ioasid_set *set, ioasid_t ioasid) > +{ > + int ret = 0; > + > + spin_lock(&ioasid_allocator_lock); > + ret = ioasid_get_locked(set, ioasid); > + spin_unlock(&ioasid_allocator_lock); > + > + return ret; > +} > +EXPORT_SYMBOL_GPL(ioasid_get); > + > +void ioasid_put_locked(struct ioasid_set *set, ioasid_t ioasid) > +{ > + struct ioasid_data *data; > + > + data = xa_load(&active_allocator->xa, ioasid); > + if (!data) { > + pr_err("Trying to put unknown IOASID %u\n", ioasid); > + return; > + } > + > + if (set && data->set != set) { > + pr_err("Trying to drop IOASID not in the set %u\n", ioasid); > + return; > + } > + > + if (!refcount_dec_and_test(&data->users)) { > + pr_debug("%s: IOASID %d has %d remainning users\n", > + __func__, ioasid, refcount_read(&data->users)); > + return; > + } > + ioasid_do_free(data); > +} > +EXPORT_SYMBOL_GPL(ioasid_put_locked); > + > +/** > + * ioasid_put - Drop a reference of an ioasid > + * @set > + * @ioasid > + * > + * Check set ownership if @set is non-null. > + */ > +void ioasid_put(struct ioasid_set *set, ioasid_t ioasid) > +{ > + spin_lock(&ioasid_allocator_lock); > + ioasid_put_locked(set, ioasid); > + spin_unlock(&ioasid_allocator_lock); > +} > +EXPORT_SYMBOL_GPL(ioasid_put); > + > +/** > * ioasid_find - Find IOASID data > * @set: the IOASID set > * @ioasid: the IOASID to find > diff --git a/include/linux/ioasid.h b/include/linux/ioasid.h > index 412d025d440e..310abe4187a3 100644 > --- a/include/linux/ioasid.h > +++ b/include/linux/ioasid.h > @@ -76,6 +76,10 @@ int ioasid_attach_data(ioasid_t ioasid, void *data); > int ioasid_register_allocator(struct ioasid_allocator_ops *allocator); > void ioasid_unregister_allocator(struct ioasid_allocator_ops *allocator); > void ioasid_is_in_set(struct ioasid_set *set, ioasid_t ioasid); > +int ioasid_get(struct ioasid_set *set, ioasid_t ioasid); > +int ioasid_get_locked(struct ioasid_set *set, ioasid_t ioasid); > +void ioasid_put(struct ioasid_set *set, ioasid_t ioasid); > +void ioasid_put_locked(struct ioasid_set *set, ioasid_t ioasid); > int ioasid_set_for_each_ioasid(struct ioasid_set *sdata, > void (*fn)(ioasid_t id, void *data), > void *data); > -- > 2.7.4 > > _______________________________________________ > iommu mailing list > iommu@lists.linux-foundation.org > https://lists.linuxfoundation.org/mailman/listinfo/iommu