From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Date: Mon, 02 Sep 2019 18:22:52 +0000 Subject: Re: [PATCH v2 2/9] x86: numa: check the node id consistently for x86 Message-Id: <20190902182252.GC35858@gmail.com> List-Id: References: <1567231103-13237-1-git-send-email-linyunsheng@huawei.com> <1567231103-13237-3-git-send-email-linyunsheng@huawei.com> <20190831085539.GG2369@hirez.programming.kicks-ass.net> <4d89c688-49e4-a2aa-32ee-65e36edcd913@huawei.com> <20190831161247.GM2369@hirez.programming.kicks-ass.net> <20190902072542.GN2369@hirez.programming.kicks-ass.net> <5fa2aa99-89fa-cd41-b090-36a23cfdeb73@huawei.com> <20190902125644.GQ2369@hirez.programming.kicks-ass.net> In-Reply-To: <20190902125644.GQ2369@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Peter Zijlstra Cc: Yunsheng Lin , 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-kernel@vger.kernel.org, mwb@linux.vnet.ibm.com, paulus@samba.org, hpa@zytor.com, sparclinux@vger.kernel.org, chenhc@lemote.com, will@kernel.org, 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, ink@jurassic.park.msu.ru, cai@lca.pw, 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, robin.murphy@arm.com, linux-mips@vger.kernel.org, ralf@linux-mips.org, tbogendoerfer@suse.de, paul.burton@mips.com, linux-alpha@vger.kernel.org, bp@alien8.de, akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org, davem@davemloft.net, Greg Kroah-Hartman , "Rafael J. Wysocki" * Peter Zijlstra wrote: > On Mon, Sep 02, 2019 at 08:25:24PM +0800, Yunsheng Lin wrote: > > On 2019/9/2 15:25, Peter Zijlstra wrote: > > > On Mon, Sep 02, 2019 at 01:46:51PM +0800, Yunsheng Lin wrote: > > >> On 2019/9/1 0:12, Peter Zijlstra wrote: > > > > > >>> 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? > > > > > > NUMA_NO_NODE := -1, which is not a valid node number. It is also, like I > > > said, not a valid device location on a NUMA system. > > > > > > Just because ACPI/BIOS is shit, doesn't mean the device doesn't have a > > > node association. It just means we don't know and might have to guess. > > > > How do we guess the device's location when ACPI/BIOS does not set it? > > See device_add(), it looks to the device's parent and on NO_NODE, puts > it there. > > Lacking any hints, just stick it to node0 and print a FW_BUG or > something. > > > It seems dev_to_node() does not do anything about that and leave the > > job to the caller or whatever function that get called with its return > > value, such as cpumask_of_node(). > > Well, dev_to_node() doesn't do anything; nor should it. It are the > callers of set_dev_node() that should be taking care. > > Also note how device_add() sets the device node to the parent device's > node on NUMA_NO_NODE. Arguably we should change it to complain when it > finds NUMA_NO_NODE and !parent. > > --- > drivers/base/core.c | 12 ++++++++++-- > 1 file changed, 10 insertions(+), 2 deletions(-) > > diff --git a/drivers/base/core.c b/drivers/base/core.c > index f0dd8e38fee3..2caf204966a0 100644 > --- a/drivers/base/core.c > +++ b/drivers/base/core.c > @@ -2120,8 +2120,16 @@ int device_add(struct device *dev) > dev->kobj.parent = kobj; > > /* use parent numa_node */ > - if (parent && (dev_to_node(dev) = NUMA_NO_NODE)) > - set_dev_node(dev, dev_to_node(parent)); > + if (dev_to_node(dev) = NUMA_NO_NODE) { > + if (parent) > + set_dev_node(dev, dev_to_node(parent)); > +#ifdef CONFIG_NUMA > + else { > + pr_err("device: '%s': has no assigned NUMA node\n", dev_name(dev)); > + set_dev_node(dev, 0); > + } > +#endif BTW., is firmware required to always provide a NUMA node on NUMA systems? I.e. do we really want this warning on non-NUMA systems that don't assign NUMA nodes? Also, even on NUMA systems, is firmware required to provide a NUMA node - i.e. is it in principle invalid to offer no NUMA binding? Thanks, Ingo