Re: [PATCH v3 21/23] KVM: s390: Enable 1M pages for gmap

Christian Borntraeger
2025-11-06T16:38:06Z

Am 06.11.25 um 17:36 schrieb Claudio Imbrenda:
> On Thu, 6 Nov 2025 17:22:33 +0100
> Christian Borntraeger <borntraeger@de.ibm.com> wrote:
>
>> Am 06.11.25 um 17:11 schrieb Claudio Imbrenda:
>>> While userspace is allowed to have pages of any size, the new gmap
>>> would always use 4k pages to back the guest.
>>>
>>> Enable 1M pages for gmap.
>>>
>>> This allows 1M pages to be used to back a guest when userspace is using
>>> 1M pages for the corresponding addresses (e.g. THP or hugetlbfs).
>>>
>>> Remove the limitation that disallowed having nested guests and
>>> hugepages at the same time.
>>
>> Nice. This might allow us to enable hpage=1 as new default as soon as
>> things stabilize.
>>
>> We would also be able to use 2GB huge pages for the qemu mapping?
>
> yes, but I don't think that userspace can have 2G THPs right now

Not THP, but hugetlbfs.