From: Yunsheng Lin <linyunsheng@huawei.com> To: Peter Zijlstra <peterz@infradead.org> Cc: <dalias@libc.org>, <linux-sh@vger.kernel.org>, <catalin.marinas@arm.com>, <dave.hansen@linux.intel.com>, <heiko.carstens@de.ibm.com>, <linuxarm@huawei.com>, <jiaxun.yang@flygoat.com>, <linux-mips@vger.kernel.org>, <mwb@linux.vnet.ibm.com>, <paulus@samba.org>, <hpa@zytor.com>, <sparclinux@vger.kernel.org>, <chenhc@lemote.com>, <will@kernel.org>, <cai@lca.pw>, <linux-s390@vger.kernel.org>, <ysato@users.sourceforge.jp>, <mpe@ellerman.id.au>, <x86@kernel.org>, <rppt@linux.ibm.com>, <borntraeger@de.ibm.com>, <dledford@redhat.com>, <mingo@redhat.com>, <jeffrey.t.kirsher@intel.com>, <benh@kernel.crashing.org>, <jhogan@kernel.org>, <nfont@linux.vnet.ibm.com>, <mattst88@gmail.com>, <len.brown@intel.com>, <gor@linux.ibm.com>, <anshuman.khandual@arm.com>, <bp@alien8.de>, <luto@kernel.org>, <tglx@linutronix.de>, <naveen.n.rao@linux.vnet.ibm.com>, <linux-arm-kernel@lists.infradead.org>, <rth@twiddle.net>, <axboe@kernel.dk>, <linuxppc-dev@lists.ozlabs.org>, <linux-kernel@vger.kernel.org>, <ralf@linux-mips.org>, <tbogendoerfer@suse.de>, <paul.burton@mips.com>, <linux-alpha@vger.kernel.org>, <ink@jurassic.park.msu.ru>, <akpm@linux-foundation.org>, <robin.murphy@arm.com>, <davem@davemloft.net> Subject: Re: [PATCH v2 2/9] x86: numa: check the node id consistently for x86 Date: Mon, 2 Sep 2019 13:46:51 +0800 Message-ID: <ae64285f-5134-4147-7b02-34bb5d519e8c@huawei.com> (raw) In-Reply-To: <20190831161247.GM2369@hirez.programming.kicks-ass.net> On 2019/9/1 0:12, Peter Zijlstra wrote: > On Sat, Aug 31, 2019 at 06:09:39PM +0800, Yunsheng Lin wrote: >> >> >> On 2019/8/31 16:55, Peter Zijlstra wrote: >>> On Sat, Aug 31, 2019 at 01:58:16PM +0800, Yunsheng Lin wrote: >>>> According to Section 6.2.14 from ACPI spec 6.3 [1], the setting >>>> of proximity domain is optional, as below: >>>> >>>> This optional object is used to describe proximity domain >>>> associations within a machine. _PXM evaluates to an integer >>>> that identifies a device as belonging to a Proximity Domain >>>> defined in the System Resource Affinity Table (SRAT). >>> >>> That's just words.. what does it actually mean? >> >> It means the dev_to_node(dev) may return -1 if the bios does not >> implement the proximity domain feature, user may use that value >> to call cpumask_of_node and cpumask_of_node does not protect itself >> from node id being -1, which causes out of bound access. > >>>> @@ -69,6 +69,12 @@ extern const struct cpumask *cpumask_of_node(int node); >>>> /* Returns a pointer to the cpumask of CPUs on Node 'node'. */ >>>> static inline const struct cpumask *cpumask_of_node(int node) >>>> { >>>> + if (node >= nr_node_ids) >>>> + return cpu_none_mask; >>>> + >>>> + if (node < 0 || !node_to_cpumask_map[node]) >>>> + return cpu_online_mask; >>>> + >>>> return node_to_cpumask_map[node]; >>>> } >>>> #endif >>> >>> I _reallly_ hate this. Users are expected to use valid numa ids. Now >>> we're adding all this checking to all users. Why do we want to do that? >> >> As above, the dev_to_node(dev) may return -1. >> >>> >>> Using '(unsigned)node >= nr_nods_ids' is an error. >> >> 'node >= nr_node_ids' can be dropped if all user is expected to not call >> cpumask_of_node with node id greater or equal to nr_nods_ids. > > you copied my typo :-) I did note the typo, corrected the first one, but missed the second one :) > >> From what I can see, the problem can be fixed in three place: >> 1. Make user dev_to_node return a valid node id even when proximity >> domain is not set by bios(or node id set by buggy bios is not valid), >> which may need info from the numa system to make sure it will return >> a valid node. >> >> 2. User that call cpumask_of_node should ensure the node id is valid >> before calling cpumask_of_node, and user also need some info to >> make ensure node id is valid. >> >> 3. Make sure cpumask_of_node deal with invalid node id as this patchset. >> >> Which one do you prefer to make sure node id is valid, or do you >> have any better idea? >> >> Any detail advice and suggestion will be very helpful, thanks. > > 1) because even it is not set, the device really does belong to a node. > It is impossible a device will have magic uniform access to memory when > CPUs cannot. So it means dev_to_node() will return either NUMA_NO_NODE or a valid node id? > > 2) is already true today, cpumask_of_node() requires a valid node_id. Ok, most of the user does check node_id before calling cpumask_of_node(), but does a little different type of checking: 1) some does " < 0" check; 2) some does "== NUMA_NO_NODE" check; 3) some does ">= MAX_NUMNODES" check; 4) some does "< 0 || >= MAX_NUMNODES || !node_online(node)" check. > > 3) is just wrong and increases overhead for everyone. Ok, cpumask_of_node() is also used in some critical path such as scheduling, which may not need those checking, the overhead is unnecessary. But for non-critical path such as setup or configuration path, it better to have consistent checking, and also simplify the user code that calls cpumask_of_node(). Do you think it is worth the trouble to add a new function such as cpumask_of_node_check(maybe some other name) to do consistent checking? Or caller just simply check if dev_to_node()'s return value is NUMA_NO_NODE before calling cpumask_of_node()? > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > > . >
next prev parent reply index Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-08-31 5:58 [PATCH v2 0/9] check the node id consistently across different arches Yunsheng Lin 2019-08-31 5:58 ` [PATCH v2 1/9] arm64: numa: check the node id consistently for arm64 Yunsheng Lin 2019-08-31 5:58 ` [PATCH v2 2/9] x86: numa: check the node id consistently for x86 Yunsheng Lin 2019-08-31 8:55 ` Peter Zijlstra 2019-08-31 10:09 ` Yunsheng Lin 2019-08-31 16:12 ` Peter Zijlstra 2019-09-01 4:45 ` Something about loongson_llsc_mb 陈华才 [not found] ` <2019090410032559707512@loongson.cn> 2019-09-04 9:21 ` Peter Zijlstra 2019-09-04 10:04 ` Peter Zijlstra 2019-09-04 12:57 ` Huang Pei 2019-09-02 5:46 ` Yunsheng Lin [this message] 2019-09-02 7:25 ` [PATCH v2 2/9] x86: numa: check the node id consistently for x86 Peter Zijlstra 2019-09-02 12:25 ` Yunsheng Lin 2019-09-02 12:56 ` Peter Zijlstra 2019-09-02 18:22 ` Ingo Molnar 2019-09-02 19:14 ` Peter Zijlstra 2019-09-03 6:19 ` Yunsheng Lin 2019-09-03 7:11 ` Peter Zijlstra 2019-09-03 8:31 ` Yunsheng Lin 2019-09-02 18:17 ` Ingo Molnar 2019-09-03 7:53 ` [PATCH] x86/mm: Fix cpumask_of_node() error condition Peter Zijlstra 2019-08-31 5:58 ` [PATCH v2 3/9] alpha: numa: check the node id consistently for alpha Yunsheng Lin 2019-08-31 5:58 ` [PATCH v2 4/9] powerpc: numa: check the node id consistently for powerpc Yunsheng Lin 2019-08-31 5:58 ` [PATCH v2 5/9] s390: numa: check the node id consistently for s390 Yunsheng Lin 2019-09-02 4:05 ` kbuild test robot 2019-08-31 5:58 ` [PATCH v2 6/9] sh: numa: check the node id consistently for sh Yunsheng Lin 2019-08-31 5:58 ` [PATCH v2 7/9] sparc64: numa: check the node id consistently for sparc64 Yunsheng Lin 2019-08-31 6:53 ` David Miller 2019-08-31 8:57 ` Yunsheng Lin 2019-08-31 20:02 ` David Miller 2019-09-02 6:08 ` Yunsheng Lin 2019-09-02 15:17 ` David Miller 2019-08-31 5:58 ` [PATCH v2 8/9] mips: numa: check the node id consistently for mips ip27 Yunsheng Lin 2019-08-31 5:58 ` [PATCH v2 9/9] mips: numa: check the node id consistently for mips loongson64 Yunsheng Lin
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