Re: [GIT PULL] VFIO updates for v6.17-rc1

[David Hildenbrand <david@redhat.com>]

On 05.08.25 16:24, Jason Gunthorpe wrote:
> On Tue, Aug 05, 2025 at 04:22:32PM +0200, David Hildenbrand wrote:
>> On 05.08.25 16:20, Jason Gunthorpe wrote:
>>> On Tue, Aug 05, 2025 at 04:10:45PM +0200, David Hildenbrand wrote:
>>>> There are some weird scenarios where you hotplug memory after boot memory,
>>>> and suddenly you can runtime-allocate a gigantic folio that spans both
>>>> ranges etc.
>>>
>>> I was thinking we'd forbid this directly, but yes it is a another new
>>> check.
>>>
>>>> So while related, the corner cases are all a bit nasty, and just forbidding
>>>> folios to span a memory section on these problematic configs (sparse
>>>> !vmemmap) sounds interesting.
>>>
>>> Indeed, this just sounds like forcing MAX_ORDER to be no larger than
>>> the section size for this old mode?
>>
>> MAX_ORDER is always limited to the section size already.
>>
>> MAX_ORDER is only about buddy allocations. What hugetlb and dax do is
>> independent of MAX_ORDER.
> 
> Oh I thought it limited folios too.
> 
> Still same idea is to have a MAX_FOLIO_ORDER for that case.

Yes. Usually unlimited, except we are in this weird config state.

-- 
Cheers,

David / dhildenb