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Tue, 30 Mar 2021 00:38:59 +0000 Received: from localhost (172.20.145.6) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Tue, 30 Mar 2021 00:38:57 +0000 From: Alistair Popple To: CC: , , , , , , , , , Alistair Popple , "kernel test robot" Subject: [PATCH v3] kernel/resource: Fix locking in request_free_mem_region Date: Tue, 30 Mar 2021 11:38:42 +1100 Message-ID: <20210330003842.18948-1-apopple@nvidia.com> X-Mailer: git-send-email 2.20.1 MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [172.20.145.6] X-ClientProxiedBy: HQMAIL111.nvidia.com (172.20.187.18) To HQMAIL107.nvidia.com (172.20.187.13) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 45070697-4b22-43da-6e4e-08d8f3143554 X-MS-TrafficTypeDiagnostic: MWHPR12MB1952: X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:9508; X-MS-Exchange-SenderADCheck: 1 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:216.228.112.34;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:schybrid03.nvidia.com;CAT:NONE;SFS:(4636009)(396003)(346002)(136003)(376002)(39860400002)(46966006)(36840700001)(86362001)(82310400003)(478600001)(1076003)(7416002)(83380400001)(36906005)(47076005)(26005)(70586007)(8936002)(426003)(5660300002)(2616005)(6666004)(82740400003)(7636003)(4326008)(16526019)(186003)(2906002)(336012)(6916009)(8676002)(54906003)(36860700001)(356005)(36756003)(70206006)(316002);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 30 Mar 2021 00:38:59.0857 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 45070697-4b22-43da-6e4e-08d8f3143554 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.112.34];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: BN8NAM11FT033.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: MWHPR12MB1952 X-Stat-Signature: 7y56kd5mp19d6pamdcc49pxosxyn7ytn X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 79D386000107 Received-SPF: none (nvidia.com>: No applicable sender policy available) receiver=imf09; identity=mailfrom; envelope-from=""; helo=NAM12-MW2-obe.outbound.protection.outlook.com; client-ip=40.107.244.62 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1617064740-734490 Content-Transfer-Encoding: quoted-printable 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: request_free_mem_region() is used to find an empty range of physical addresses for hotplugging ZONE_DEVICE memory. It does this by iterating over the range of possible addresses using region_intersects() to see if the range is free. region_intersects() obtains a read lock before walking the resource tree to protect against concurrent changes. However it drops the lock prior to returning. This means by the time request_mem_region() is called in request_free_mem_region() another thread may have already reserved the requested region resulting in unexpected failures and a message in the kernel log from hitting this condition: /* * mm/hmm.c reserves physical addresses which then * become unavailable to other users. Conflicts are * not expected. Warn to aid debugging if encountered. */ if (conflict->desc =3D=3D IORES_DESC_DEVICE_PRIVATE_MEMORY) { pr_warn("Unaddressable device %s %pR conflicts with %pR", conflict->name, conflict, res); To fix this create versions of region_intersects() and request_mem_region() that allow the caller to take the appropriate lock such that it may be held over the required calls. Instead of creating another version of devm_request_mem_region() that doesn't take the lock open-code it to allow the caller to pre-allocate the required memory prior to taking the lock. Fixes: 0c385190392d8 ("resource: add a not device managed request_free_me= m_region variant") Fixes: 0092908d16c60 ("mm: factor out a devm_request_free_mem_region help= er") Fixes: 4ef589dc9b10c ("mm/hmm/devmem: device memory hotplug using ZONE_DE= VICE") Signed-off-by: Alistair Popple Acked-by: Balbir Singh Reported-by: kernel test robot --- Hi Andrew, This fixes a boot issue reported by the kernel test robot with the previous version of the patch on x86 with CONFIG_IO_STRICT_DEVMEM=3Dy. This was due to the platform specific implementation of devmem_is_allowed() creating a recursive lock which I missed. I notice you have put v2 in mmtom so apologies for the churn but can you please use this version instead? Thanks. - Alistair --- kernel/resource.c | 142 ++++++++++++++++++++++++++++++---------------- 1 file changed, 92 insertions(+), 50 deletions(-) diff --git a/kernel/resource.c b/kernel/resource.c index 627e61b0c124..7061b9f903ca 100644 --- a/kernel/resource.c +++ b/kernel/resource.c @@ -523,6 +523,34 @@ int __weak page_is_ram(unsigned long pfn) } EXPORT_SYMBOL_GPL(page_is_ram); =20 +static int __region_intersects(resource_size_t start, size_t size, + unsigned long flags, unsigned long desc) +{ + struct resource res; + int type =3D 0; int other =3D 0; + struct resource *p; + + res.start =3D start; + res.end =3D start + size - 1; + + for (p =3D iomem_resource.child; p ; p =3D p->sibling) { + bool is_type =3D (((p->flags & flags) =3D=3D flags) && + ((desc =3D=3D IORES_DESC_NONE) || + (desc =3D=3D p->desc))); + + if (resource_overlaps(p, &res)) + is_type ? type++ : other++; + } + + if (type =3D=3D 0) + return REGION_DISJOINT; + + if (other =3D=3D 0) + return REGION_INTERSECTS; + + return REGION_MIXED; +} + /** * region_intersects() - determine intersection of region with known res= ources * @start: region start address @@ -546,31 +574,12 @@ EXPORT_SYMBOL_GPL(page_is_ram); int region_intersects(resource_size_t start, size_t size, unsigned long = flags, unsigned long desc) { - struct resource res; - int type =3D 0; int other =3D 0; - struct resource *p; - - res.start =3D start; - res.end =3D start + size - 1; + int rc; =20 read_lock(&resource_lock); - for (p =3D iomem_resource.child; p ; p =3D p->sibling) { - bool is_type =3D (((p->flags & flags) =3D=3D flags) && - ((desc =3D=3D IORES_DESC_NONE) || - (desc =3D=3D p->desc))); - - if (resource_overlaps(p, &res)) - is_type ? type++ : other++; - } + rc =3D __region_intersects(start, size, flags, desc); read_unlock(&resource_lock); - - if (type =3D=3D 0) - return REGION_DISJOINT; - - if (other =3D=3D 0) - return REGION_INTERSECTS; - - return REGION_MIXED; + return rc; } EXPORT_SYMBOL_GPL(region_intersects); =20 @@ -1171,31 +1180,16 @@ struct address_space *iomem_get_mapping(void) return smp_load_acquire(&iomem_inode)->i_mapping; } =20 -/** - * __request_region - create a new busy resource region - * @parent: parent resource descriptor - * @start: resource start address - * @n: resource region size - * @name: reserving caller's ID string - * @flags: IO resource flags - */ -struct resource * __request_region(struct resource *parent, - resource_size_t start, resource_size_t n, - const char *name, int flags) +static bool request_region_locked(struct resource *parent, + struct resource *res, resource_size_t start, + resource_size_t n, const char *name, int flags) { DECLARE_WAITQUEUE(wait, current); - struct resource *res =3D alloc_resource(GFP_KERNEL); - struct resource *orig_parent =3D parent; - - if (!res) - return NULL; =20 res->name =3D name; res->start =3D start; res->end =3D start + n - 1; =20 - write_lock(&resource_lock); - for (;;) { struct resource *conflict; =20 @@ -1230,14 +1224,37 @@ struct resource * __request_region(struct resourc= e *parent, write_lock(&resource_lock); continue; } + return false; + } + + return true; +} + +/** + * __request_region - create a new busy resource region + * @parent: parent resource descriptor + * @start: resource start address + * @n: resource region size + * @name: reserving caller's ID string + * @flags: IO resource flags + */ +struct resource *__request_region(struct resource *parent, + resource_size_t start, resource_size_t n, + const char *name, int flags) +{ + struct resource *res =3D alloc_resource(GFP_KERNEL); + + if (!res) + return NULL; + + write_lock(&resource_lock); + if (!request_region_locked(parent, res, start, n, name, flags)) { /* Uhhuh, that didn't work out.. */ free_resource(res); res =3D NULL; - break; } write_unlock(&resource_lock); - - if (res && orig_parent =3D=3D &iomem_resource) + if (res && parent =3D=3D &iomem_resource) revoke_iomem(res); =20 return res; @@ -1779,26 +1796,51 @@ static struct resource *__request_free_mem_region= (struct device *dev, { resource_size_t end, addr; struct resource *res; + struct region_devres *dr =3D NULL; + + res =3D alloc_resource(GFP_KERNEL); + if (!res) + return ERR_PTR(-ENOMEM); + + if (dev) { + dr =3D devres_alloc(devm_region_release, sizeof(struct region_devres), + GFP_KERNEL); + if (!dr) { + free_resource(res); + return ERR_PTR(-ENOMEM); + } + } =20 size =3D ALIGN(size, 1UL << PA_SECTION_SHIFT); end =3D min_t(unsigned long, base->end, (1UL << MAX_PHYSMEM_BITS) - 1); addr =3D end - size + 1UL; =20 + write_lock(&resource_lock); for (; addr > size && addr >=3D base->start; addr -=3D size) { - if (region_intersects(addr, size, 0, IORES_DESC_NONE) !=3D + if (__region_intersects(addr, size, 0, IORES_DESC_NONE) !=3D REGION_DISJOINT) continue; =20 - if (dev) - res =3D devm_request_mem_region(dev, addr, size, name); - else - res =3D request_mem_region(addr, size, name); - if (!res) - return ERR_PTR(-ENOMEM); + if (!request_region_locked(&iomem_resource, res, addr, + size, name, 0)) + break; + res->desc =3D IORES_DESC_DEVICE_PRIVATE_MEMORY; + if (dev) { + dr->parent =3D &iomem_resource; + dr->start =3D addr; + dr->n =3D size; + devres_add(dev, dr); + } + + write_unlock(&resource_lock); + revoke_iomem(res); return res; } =20 + write_unlock(&resource_lock); + free_resource(res); + return ERR_PTR(-ERANGE); } =20 --=20 2.20.1