> -----Original Message-----
> From: Greg KH [mailto:gre...@linuxfoundation.org]
> Sent: Tuesday, June 2, 2020 4:24 PM
> To: Song Bao Hua (Barry Song) <song.bao....@hisilicon.com>
> Cc: raf...@kernel.org; io...@lists.linux-foundation.org;
> linux-arm-ker...@lists.infradead.org; linux-kernel@vger.kernel.org; Linuxarm
> <linux...@huawei.com>; Zengtao (B) <prime.z...@hisilicon.com>; Robin
> Murphy <robin.mur...@arm.com>
> Subject: Re: [PATCH] driver core: platform: expose numa_node to users in sysfs
>
> On Tue, Jun 02, 2020 at 03:01:39PM +1200, Barry Song wrote:
> > For some platform devices like iommu, particually ARM smmu, users may
> > care about the numa locality. for example, if threads and drivers run
> > near iommu, they may get much better performance on dma_unmap_sg.
> > For other platform devices, users may still want to know the hardware
> > topology.
> >
> > Cc: Prime Zeng <prime.z...@hisilicon.com>
> > Cc: Robin Murphy <robin.mur...@arm.com>
> > Signed-off-by: Barry Song <song.bao....@hisilicon.com>
> > ---
> > drivers/base/platform.c | 26 +++++++++++++++++++++++++-
> > 1 file changed, 25 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/base/platform.c b/drivers/base/platform.c
> > index b27d0f6c18c9..7794b9a38d82 100644
> > --- a/drivers/base/platform.c
> > +++ b/drivers/base/platform.c
> > @@ -1062,13 +1062,37 @@ static ssize_t driver_override_show(struct
> device *dev,
> > }
> > static DEVICE_ATTR_RW(driver_override);
> >
> > +static ssize_t numa_node_show(struct device *dev,
> > + struct device_attribute *attr, char *buf)
> > +{
> > + return sprintf(buf, "%d\n", dev_to_node(dev));
> > +}
> > +static DEVICE_ATTR_RO(numa_node);
> > +
> > +static umode_t platform_dev_attrs_visible(struct kobject *kobj, struct
> attribute *a,
> > + int n)
> > +{
> > + struct device *dev = container_of(kobj, typeof(*dev), kobj);
> > +
> > + if (a == &dev_attr_numa_node.attr &&
> > + dev_to_node(dev) == NUMA_NO_NODE)
> > + return 0;
> > +
> > + return a->mode;
> > +}
> >
> > static struct attribute *platform_dev_attrs[] = {
> > &dev_attr_modalias.attr,
> > + &dev_attr_numa_node.attr,
> > &dev_attr_driver_override.attr,
> > NULL,
> > };
> > -ATTRIBUTE_GROUPS(platform_dev);
> > +
> > +static struct attribute_group platform_dev_group = {
> > + .attrs = platform_dev_attrs,
> > + .is_visible = platform_dev_attrs_visible,
> > +};
> > +__ATTRIBUTE_GROUPS(platform_dev);
> >
> > static int platform_uevent(struct device *dev, struct kobj_uevent_env *env)
> > {
>
> Platform devices are NUMA? That's crazy, and feels like a total abuse
> of platform devices and drivers that really should belong on a "real"
> bus.
I am not sure if it is an abuse of platform device. But smmu is a platform
device,
drivers/iommu/arm-smmu-v3.c is a platform driver.
In a typical ARM server, there are maybe multiple SMMU devices which can support
IO virtual address and page tables for other devices on PCI-like busses.
Each different SMMU device might be close to different NUMA node. There is
really a hardware topology.
If you have multiple CPU packages in a NUMA server, some platform devices might
Belong to CPU0, some other might belong to CPU1.
-barry
>
> What drivers in the kernel today have this issue?
>
> thanks,
>
> greg k-h
