Re: [PATCH v5 08/23] KVM: s390: KVM page table management functions: allocation

[Janosch Frank <frankja@linux.ibm.com>]

On 11/24/25 13:41, Claudio Imbrenda wrote:
> On Mon, 24 Nov 2025 13:27:24 +0100
> Janosch Frank <frankja@linux.ibm.com> wrote:
> 
>> On 11/24/25 12:55, Claudio Imbrenda wrote:
>>> Add page table management functions to be used for KVM guest (gmap)
>>> page tables.
>>>
>>> This patch adds the boilerplate and functions for the allocation and
>>> deallocation of DAT tables.
>>>
>>> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
>>
>> What's the cache for, why did you add it?
> 
> the cache is needed to allocate memory when we can sleep (to avoid
> atomic allocations), and use it when holding spinlocks (when we can't
> sleep).
> 
> this is similar to what other architectures do, except that in their
> case they only have one type of page table to worry about, we need at
> least 3 types of objects.
> 
> unlike other architectures, allocations from the cache can fail, and
> the calling code needs to handle failures (e.g. by replenishing the
> cache and trying again)

Well, this information should make it into this patch, either into the 
description or in the body.

> 
>>
>>> ---
>>>    arch/s390/kvm/Makefile     |   1 +
>>>    arch/s390/kvm/dat.c        | 103 +++++++++++++++++++++++++++++++++++++
>>>    arch/s390/kvm/dat.h        |  77 +++++++++++++++++++++++++++
>>>    arch/s390/mm/page-states.c |   1 +
>>>    4 files changed, 182 insertions(+)
>>>    create mode 100644 arch/s390/kvm/dat.c