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Re: [PATCH 1/2] x86/mm: avoid phys_to_nid() calls for invalid addresses
- To: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Mon, 19 Dec 2022 08:14:38 +0100
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- Cc: George Dunlap <George.Dunlap@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Roger Pau Monne <roger.pau@xxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Mon, 19 Dec 2022 07:14:48 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 16.12.2022 20:24, Andrew Cooper wrote:
> On 13/12/2022 11:36 am, Jan Beulich wrote:
>> RFC: With small enough a NUMA hash shift it would still be possible to
>> hit an SRAT hole, despite mfn_valid() passing. Hence, like was the
>> original plan, it may still be necessary to relax the checking in
>> phys_to_nid() (or its designated replacements). At which point the
>> value of this change here would shrink to merely reducing the
>> chance of unintentionally doing NUMA_NO_NODE allocations.
>
> Why does the NUMA shift matter? Can't this occur for badly constructed
> SRAT tables too?
Well, the NUMA hash shift is computed from the SRAT table entries, so
often "badly constructed" => "too small shift".
> Nevertheless, this is a clear improvement over what's currently in tree,
> so I'm going to commit it to try and unblock OSSTest. The tree has been
> blocked for too long. Further adjustments can come in due course.
Thanks. And I see it has unblocked the tree.
Jan
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