RE: [PATCH v3 5/6] device-dax: use fallback nid when numa_node is invalid

[Justin He]

Hi Dan

> -----Original Message-----
> From: Dan Williams <dan.j.williams@xxxxxxxxx>
> Sent: Thursday, July 9, 2020 11:39 AM
> To: Justin He <Justin.He@xxxxxxx>
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> Subject: Re: [PATCH v3 5/6] device-dax: use fallback nid when numa_node is
> invalid
> 
> On Wed, Jul 8, 2020 at 7:07 PM Jia He <justin.he@xxxxxxx> wrote:
> >
> > numa_off is set unconditionally at the end of dummy_numa_init(),
> > even with a fake numa node. ACPI detects node id as NUMA_NO_NODE(-1) in
> > acpi_map_pxm_to_node() because it regards numa_off as turning off the
> numa
> > node. Hence dev_dax->target_node is NUMA_NO_NODE on arm64 with fake numa.
> >
> > Without this patch, pmem can't be probed as a RAM device on arm64 if
> SRAT table
> > isn't present:
> > $ndctl create-namespace -fe namespace0.0 --mode=devdax --map=dev -s 1g -
> a 64K
> > kmem dax0.0: rejecting DAX region [mem 0x240400000-0x2bfffffff] with
> invalid node: -1
> > kmem: probe of dax0.0 failed with error -22
> >
> > This fixes it by using fallback memory_add_physaddr_to_nid() as nid.
> >
> > Suggested-by: David Hildenbrand <david@xxxxxxxxxx>
> > Signed-off-by: Jia He <justin.he@xxxxxxx>
> > ---
> >  drivers/dax/kmem.c | 21 +++++++++++++--------
> >  1 file changed, 13 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
> > index 275aa5f87399..218f66057994 100644
> > --- a/drivers/dax/kmem.c
> > +++ b/drivers/dax/kmem.c
> > @@ -31,22 +31,23 @@ int dev_dax_kmem_probe(struct device *dev)
> >         int numa_node;
> >         int rc;
> >
> > +       /* Hotplug starting at the beginning of the next block: */
> > +       kmem_start = ALIGN(res->start, memory_block_size_bytes());
> > +
> >         /*
> >          * Ensure good NUMA information for the persistent memory.
> >          * Without this check, there is a risk that slow memory
> >          * could be mixed in a node with faster memory, causing
> > -        * unavoidable performance issues.
> > +        * unavoidable performance issues. Furthermore, fallback node
> > +        * id can be used when numa_node is invalid.
> >          */
> >         numa_node = dev_dax->target_node;
> >         if (numa_node < 0) {
> > -               dev_warn(dev, "rejecting DAX region %pR with invalid
> node: %d\n",
> > -                        res, numa_node);
> > -               return -EINVAL;
> > +               numa_node = memory_add_physaddr_to_nid(kmem_start);
> 
> I think this fixup belongs to the core to set a fallback value for
> dev_dax->target_node.
> 
> I'm close to having patches to provide a functional
> phys_addr_to_target_node() for arm64.

Should My this patch(5/6) wait on your new phys_addr_to_target_node() patch?
Thanks for the clarification.

--
Cheers,
Justin (Jia He)