linux-kernel - Re: [PATCH v3] driver core: platform: expose numa

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Message-ID: <dc66d5a7-fa26-4c56-7445-57f99d3a5018@huawei.com>
Date:   Mon, 22 Jun 2020 11:48:44 +0100
From:   John Garry <john.garry@...wei.com>
To:     Barry Song <song.bao.hua@...ilicon.com>,
        <gregkh@...uxfoundation.org>, <rafael@...nel.org>
CC:     Robin Murphy <robin.murphy@....com>,
        <linux-kernel@...r.kernel.org>,
        Prime Zeng <prime.zeng@...ilicon.com>, <linuxarm@...wei.com>
Subject: Re: [PATCH v3] driver core: platform: expose numa_node to users in
 sysfs

On 19/06/2020 04:00, Barry Song wrote:
> Some platform devices like ARM SMMU are memory-mapped and populated by ACPI/IORT.
> In this case, NUMA topology of those platform devices are exported by firmware as
> well. Software might care about the numa_node of those devices in order to achieve
> NUMA locality.

Is it generally the case that the SMMU will be in the same NUMA node as 
the endpoint device (which you're driving)? If so, we can get this info 
from sysfs already for the endpoint, and also have a link from the 
endpoint to the iommu for pci devices (which I assume you're interested in):

root@(none)$ ls -l /sys/devices/pci0000:74/0000:74:02.0/ | grep iommu
lrwxrwxrwx 1 root  root 0 Jun 22 10:33 iommu -> 
../../platform/arm-smmu-v3.2.auto/iommu/smmu3.0x0000000140000000
lrwxrwxrwx 1 root  root 0 Jun 22 10:33 iommu_group -> 
../../../kernel/iommu_groups/0
root@(none)$

Thanks,
John