Messages in this thread | | | Subject | Re: [PATCH RFC] driver core: ensure a device has valid node id in device_add() | From | Yunsheng Lin <> | Date | Sat, 7 Sep 2019 10:10:34 +0800 |
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On 2019/9/6 22:00, Greg KH wrote: > On Fri, Sep 06, 2019 at 04:21:47PM +0800, Yunsheng Lin wrote: >> On 2019/9/6 14:52, Greg KH wrote: >>> On Fri, Sep 06, 2019 at 02:41:36PM +0800, Yunsheng Lin wrote: >>>> On 2019/9/5 15:33, Greg KH wrote: >>>>> On Thu, Sep 05, 2019 at 02:48:24PM +0800, Yunsheng Lin wrote: >>>>>> On 2019/9/5 13:57, Greg KH wrote: >>>>>>> On Thu, Sep 05, 2019 at 09:33:50AM +0800, Yunsheng Lin wrote: >>>>>>>> Currently a device does not belong to any of the numa nodes >>>>>>>> (dev->numa_node is NUMA_NO_NODE) when the FW does not provide >>>>>>>> the node id and the device has not no parent device. >>>>>>>> >>>>>>>> According to discussion in [1]: >>>>>>>> Even if a device's numa node is not set by fw, the device >>>>>>>> really does belong to a node. >>>>>>>> >>>>>>>> This patch sets the device node to node 0 in device_add() if >>>>>>>> the fw has not specified the node id and it either has no >>>>>>>> parent device, or the parent device also does not have a valid >>>>>>>> node id. >>>>>>>> >>>>>>>> There may be explicit handling out there relying on NUMA_NO_NODE, >>>>>>>> like in nvme_probe(). >>>>>>>> >>>>>>>> [1] https://lkml.org/lkml/2019/9/2/466 >>>>>>>> >>>>>>>> Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com> >>>>>>>> --- >>>>>>>> drivers/base/core.c | 17 ++++++++++++++--- >>>>>>>> include/linux/numa.h | 2 ++ >>>>>>>> 2 files changed, 16 insertions(+), 3 deletions(-) >>>>>>>> >>>>>>>> diff --git a/drivers/base/core.c b/drivers/base/core.c >>>>>>>> index 1669d41..466b8ff 100644 >>>>>>>> --- a/drivers/base/core.c >>>>>>>> +++ b/drivers/base/core.c >>>>>>>> @@ -2107,9 +2107,20 @@ int device_add(struct device *dev) >>>>>>>> if (kobj) >>>>>>>> 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)); >>>>>>>> + /* use parent numa_node or default node 0 */ >>>>>>>> + if (!numa_node_valid(dev_to_node(dev))) { >>>>>>>> + int nid = parent ? dev_to_node(parent) : NUMA_NO_NODE; >>>>>>> >>>>>>> Can you expand this to be a "real" if statement please? >>>>>> >>>>>> Sure. May I ask why "? :" is not appropriate here? >>>>> >>>>> Because it is a pain to read, just spell it out and make it obvious what >>>>> is happening. You write code for developers first, and the compiler >>>>> second, and in this case, either way is identical to the compiler. >>>>> >>>>>>>> + >>>>>>>> + if (numa_node_valid(nid)) { >>>>>>>> + set_dev_node(dev, nid); >>>>>>>> + } else { >>>>>>>> + if (nr_node_ids > 1U) >>>>>>>> + pr_err("device: '%s': has invalid NUMA node(%d)\n", >>>>>>>> + dev_name(dev), dev_to_node(dev)); >>>>>>> >>>>>>> dev_err() will show you the exact device properly, instead of having to >>>>>>> rely on dev_name(). >>>>>>> >>>>>>> And what is a user to do if this message happens? How do they fix this? >>>>>>> If they can not, what good is this error message? >>>>>> >>>>>> If user know about their system's topology well enough and node 0 >>>>>> is not the nearest node to the device, maybe user can readjust that by >>>>>> writing the nearest node to /sys/class/pci_bus/XXXX/device/numa_node, >>>>>> if not, then maybe user need to contact the vendor for info or updates. >>>>>> >>>>>> Maybe print error message as below: >>>>>> >>>>>> dev_err(dev, FW_BUG "has invalid NUMA node(%d). Readjust it by writing to sysfs numa_node or contact your vendor for updates.\n", >>>>>> dev_to_node(dev)); >>>>> >>>>> FW_BUG? >>>>> >>>>> Anyway, if you make this change, how many machines start reporting this >>>>> error? >>>> >>>> Any machines with more than one numa node will start reporting this error. >>>> >>>> 1) many virtual deivces maybe do not set the node id before calling >>>> device_register(), such as vfio, tun, etc. >>>> >>>> 2) struct cpu has a dev, but does not set the dev' node according to >>>> cpu_to_node(). >>>> >>>> 3) Many platform Device also do not have a node id provided by FW. >>> >>> Then this patch is not ok, as you are flooding the kernel log saying the >>> system is "broken" when this is just what it always has been like. How >>> is anyone going to "fix" things? >> >> cpu->node_id does not seem to be used, maybe we can fix the cpu device: >> >> diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c >> index cc37511d..ad0a841 100644 >> --- a/drivers/base/cpu.c >> +++ b/drivers/base/cpu.c >> @@ -41,7 +41,7 @@ static void change_cpu_under_node(struct cpu *cpu, >> int cpuid = cpu->dev.id; >> unregister_cpu_under_node(cpuid, from_nid); >> register_cpu_under_node(cpuid, to_nid); >> - cpu->node_id = to_nid; >> + set_dev_node(&cpu->dev, to_nid); >> } >> >> static int cpu_subsys_online(struct device *dev) >> @@ -367,7 +367,7 @@ int register_cpu(struct cpu *cpu, int num) >> { >> int error; >> >> - cpu->node_id = cpu_to_node(num); >> + set_dev_node(&cpu->dev, cpu_to_node(num)); >> memset(&cpu->dev, 0x00, sizeof(struct device)); >> cpu->dev.id = num; >> cpu->dev.bus = &cpu_subsys; >> diff --git a/include/linux/cpu.h b/include/linux/cpu.h >> index fcb1386..9a6fc51 100644 >> --- a/include/linux/cpu.h >> +++ b/include/linux/cpu.h >> @@ -24,7 +24,6 @@ struct device_node; >> struct attribute_group; >> >> struct cpu { >> - int node_id; /* The node which contains the CPU */ >> int hotpluggable; /* creates sysfs control file if hotpluggable */ >> struct device dev; >> }; > > I have no idea what you are trying to do here, it feels like you are > flailing around trying to set something that almost no bios/firmware > sets or cares about.
The above isn't related to my problem really.
It just that there may be three fields that can indicate the node id of a cpu: per_cpu(numa_node), cpu->node_id and cpu->dev.numa_node
The per_cpu(numa_node) may be used for the fast path, and cpu->node_id does not seems to be used, so it can be removed when cpu->dev.numa_node is there.
Anyway, this is different problem here, maybe a separate patch to "fix" it or clean it up if the above makes sense to you.
Sorry for the confusion.
> > If setting the proper node is a requirement, make sure your firmware > does this and then all should be fine. Otherwise just use the default > node like what happens today, right?
Yes
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