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pr=C From: Vikram Garhwal To: CC: , , , Subject: [XEN][PATCH v10 14/20] common/device_tree: Add rwlock for dt_host Date: Fri, 25 Aug 2023 01:02:16 -0700 Message-ID: <20230825080222.14247-15-vikram.garhwal@amd.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20230825080222.14247-1-vikram.garhwal@amd.com> References: <20230825080222.14247-1-vikram.garhwal@amd.com> MIME-Version: 1.0 X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CO1PEPF000044F8:EE_|SN7PR12MB6813:EE_ X-MS-Office365-Filtering-Correlation-Id: 17ee52d9-2f6c-4647-bf61-08dba541b7bc X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:CAL;SFV:NSPM;H:SATLEXMB03.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230031)(4636009)(346002)(39860400002)(136003)(396003)(376002)(186009)(1800799009)(82310400011)(451199024)(40470700004)(46966006)(36840700001)(54906003)(70586007)(70206006)(316002)(6916009)(81166007)(478600001)(40480700001)(26005)(6666004)(82740400003)(41300700001)(86362001)(2906002)(356005)(4326008)(8676002)(8936002)(83380400001)(2616005)(40460700003)(5660300002)(47076005)(44832011)(1076003)(426003)(336012)(36756003)(36860700001)(36900700001);DIR:OUT;SFP:1101; X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 25 Aug 2023 08:03:07.5708 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 17ee52d9-2f6c-4647-bf61-08dba541b7bc X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[SATLEXMB03.amd.com] X-MS-Exchange-CrossTenant-AuthSource: CO1PEPF000044F8.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SN7PR12MB6813 Dynamic programming ops will modify the dt_host and there might be other functions which are browsing the dt_host at the same time. To avoid the race conditions, adding rwlock for browsing the dt_host during runtime. dt_host writer will be added in the follow-up patch for device tree overlay functionalities." Reason behind adding rwlock instead of spinlock: For now, dynamic programming is the sole modifier of dt_host in Xen during run time. All other access functions like iommu_release_dt_device() are just reading the dt_host during run-time. So, there is a need to protect others from browsing the dt_host while dynamic programming is modifying it. rwlock is better suitable for this task as spinlock won't be able to differentiate between read and write access. Signed-off-by: Vikram Garhwal Reviewed-by: Michal Orzel --- Changes from v9: Update commit message and fix indentation. Add ASSERT() for iommu_deassign_dt_device() and iommu_remove_dt_device(). Fix code styles. Remove rwlock_init in unflatten_device_tree() and do DEFINE_RWLOCK in device-tree.c Changes from v7: Keep one lock for dt_host instead of lock for each node under dt_host. --- --- xen/common/device_tree.c | 1 + xen/drivers/passthrough/device_tree.c | 24 ++++++++++++++++++++++-- xen/include/xen/device_tree.h | 7 +++++++ 3 files changed, 30 insertions(+), 2 deletions(-) diff --git a/xen/common/device_tree.c b/xen/common/device_tree.c index f38f51ec0b..b1c2952951 100644 --- a/xen/common/device_tree.c +++ b/xen/common/device_tree.c @@ -31,6 +31,7 @@ dt_irq_xlate_func dt_irq_xlate; struct dt_device_node *dt_host; /* Interrupt controller node*/ const struct dt_device_node *dt_interrupt_controller; +DEFINE_RWLOCK(dt_host_lock); /** * struct dt_alias_prop - Alias property in 'aliases' node diff --git a/xen/drivers/passthrough/device_tree.c b/xen/drivers/passthrough/device_tree.c index 3fad65fb69..b81dab5a48 100644 --- a/xen/drivers/passthrough/device_tree.c +++ b/xen/drivers/passthrough/device_tree.c @@ -62,6 +62,8 @@ int iommu_deassign_dt_device(struct domain *d, struct dt_device_node *dev) const struct domain_iommu *hd = dom_iommu(d); int rc; + ASSERT(rw_is_locked(&dt_host_lock)); + if ( !is_iommu_enabled(d) ) return -EINVAL; @@ -114,6 +116,8 @@ int iommu_release_dt_devices(struct domain *d) if ( !is_iommu_enabled(d) ) return 0; + read_lock(&dt_host_lock); + list_for_each_entry_safe(dev, _dev, &hd->dt_devices, domain_list) { rc = iommu_deassign_dt_device(d, dev); @@ -121,10 +125,14 @@ int iommu_release_dt_devices(struct domain *d) { dprintk(XENLOG_ERR, "Failed to deassign %s in domain %u\n", dt_node_full_name(dev), d->domain_id); + read_unlock(&dt_host_lock); + return rc; } } + read_unlock(&dt_host_lock); + return 0; } @@ -134,6 +142,8 @@ int iommu_remove_dt_device(struct dt_device_node *np) struct device *dev = dt_to_dev(np); int rc; + ASSERT(rw_is_locked(&dt_host_lock)); + if ( !iommu_enabled ) return 1; @@ -251,6 +261,8 @@ int iommu_do_dt_domctl(struct xen_domctl *domctl, struct domain *d, int ret; struct dt_device_node *dev; + read_lock(&dt_host_lock); + switch ( domctl->cmd ) { case XEN_DOMCTL_assign_device: @@ -294,7 +306,10 @@ int iommu_do_dt_domctl(struct xen_domctl *domctl, struct domain *d, spin_unlock(&dtdevs_lock); if ( d == dom_io ) - return -EINVAL; + { + ret = -EINVAL; + break; + } ret = iommu_add_dt_device(dev); if ( ret < 0 ) @@ -332,7 +347,10 @@ int iommu_do_dt_domctl(struct xen_domctl *domctl, struct domain *d, break; if ( d == dom_io ) - return -EINVAL; + { + ret = -EINVAL; + break; + } ret = iommu_deassign_dt_device(d, dev); @@ -347,5 +365,7 @@ int iommu_do_dt_domctl(struct xen_domctl *domctl, struct domain *d, break; } + read_unlock(&dt_host_lock); + return ret; } diff --git a/xen/include/xen/device_tree.h b/xen/include/xen/device_tree.h index 44d315c8ba..a262bba2ed 100644 --- a/xen/include/xen/device_tree.h +++ b/xen/include/xen/device_tree.h @@ -18,6 +18,7 @@ #include #include #include +#include #define DEVICE_TREE_MAX_DEPTH 16 @@ -218,6 +219,12 @@ extern struct dt_device_node *dt_host; */ extern const struct dt_device_node *dt_interrupt_controller; +/* + * Lock that protects r/w updates to unflattened device tree i.e. dt_host during + * runtime. Lock may not be taken for boot only code. + */ +extern rwlock_t dt_host_lock; + /** * Find the interrupt controller * For the moment we handle only one interrupt controller: the first