linux-kernel - Re: [PATCH v1] virtio_pmem: populate numa information

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Message-ID: <CAM9Jb+ggq5L9XZZHhfA98XDO+P=8y-mT+ct0JFAtXRbsCuORsA@mail.gmail.com>
Date:   Fri, 21 Oct 2022 13:42:28 +0200
From:   Pankaj Gupta <pankaj.gupta.linux@...il.com>
To:     Michael Sammler <sammler@...gle.com>
Cc:     Dan Williams <dan.j.williams@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Pasha Tatashin <pasha.tatashin@...een.com>,
        nvdimm@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] virtio_pmem: populate numa information

> Compute the numa information for a virtio_pmem device from the memory
> range of the device. Previously, the target_node was always 0 since
> the ndr_desc.target_node field was never explicitly set. The code for
> computing the numa node is taken from cxl_pmem_region_probe in
> drivers/cxl/pmem.c.
>
> Signed-off-by: Michael Sammler <sammler@...gle.com>
> ---
>  drivers/nvdimm/virtio_pmem.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/nvdimm/virtio_pmem.c b/drivers/nvdimm/virtio_pmem.c
> index 20da455d2ef6..a92eb172f0e7 100644
> --- a/drivers/nvdimm/virtio_pmem.c
> +++ b/drivers/nvdimm/virtio_pmem.c
> @@ -32,7 +32,6 @@ static int init_vq(struct virtio_pmem *vpmem)
>  static int virtio_pmem_probe(struct virtio_device *vdev)
>  {
>         struct nd_region_desc ndr_desc = {};
> -       int nid = dev_to_node(&vdev->dev);
>         struct nd_region *nd_region;
>         struct virtio_pmem *vpmem;
>         struct resource res;
> @@ -79,7 +78,15 @@ static int virtio_pmem_probe(struct virtio_device *vdev)
>         dev_set_drvdata(&vdev->dev, vpmem->nvdimm_bus);
>
>         ndr_desc.res = &res;
> -       ndr_desc.numa_node = nid;
> +
> +       ndr_desc.numa_node = memory_add_physaddr_to_nid(res.start);
> +       ndr_desc.target_node = phys_to_target_node(res.start);
> +       if (ndr_desc.target_node == NUMA_NO_NODE) {
> +               ndr_desc.target_node = ndr_desc.numa_node;
> +               dev_dbg(&vdev->dev, "changing target node from %d to %d",
> +                       NUMA_NO_NODE, ndr_desc.target_node);
> +       }

As this memory later gets hotplugged using "devm_memremap_pages". I don't
see if 'target_node' is used for fsdax case?

It seems to me "target_node" is used mainly for volatile range above
persistent memory ( e.g kmem driver?).

Thanks,
Pankaj

> +
>         ndr_desc.flush = async_pmem_flush;
>         ndr_desc.provider_data = vdev;
>         set_bit(ND_REGION_PAGEMAP, &ndr_desc.flags);
> --