[PATCH 0/4] KVM: s390: replace page allocator calls with kzalloc()

[Mike Rapoport (Microsoft)]

This is a (small) part of larger work of replacing page allocator calls
with kmalloc.

My initial intention a few month ago was to remove ugly casts [1], but then
willy pointed out that Linus objected to something like this [2] and it
looks like more than a decade old technical debt.

Largely, anything that doesn't need struct page (or a memdesc in the
future) should just use kmalloc() or kvmalloc() to allocate memory.
kmalloc() guarantees alignment, physical contiguity and working
virt_to_phys() and beside nicer API that returns void * on alloc and
doesn't require to know the allocation size on free, kmalloc() provides
better debugging capabilities than page allocator.

Another thing is that touching these allocation sites gives the reviewers
opportunity to see if a PAGE_SIZE buffer is actually needed or maybe
another size is appropriate.

For larger allocations that don't need physically contiguous memory
kvmalloc() can be a better option that __get_free_pages() because under
memory pressure it's is easier to allocate several order-0 pages than a
physically contiguous chunk with the same number of pages.

And last, but not least, removing needless calls to page allocator should
help with memdesc (aka project folio) conversion. There will be way less
places to audit to see if the user was actually using struct page.

Also in git:
https://git.kernel.org/pub/scm/linux/kernel/git/rppt/linux.git gfp-to-kmalloc/s390-kvm

[1] https://lore.kernel.org/all/20251018093002.3660549-1-rppt@xxxxxxxxxx/
[2] https://lore.kernel.org/all/CA+55aFwp4iy4rtX2gE2WjBGFL=NxMVnoFeHqYa2j1dYOMMGqxg@xxxxxxxxxxxxxx/

---
Mike Rapoport (Microsoft) (4):
      KVM: s390: Replace get_zeroed_page() with kzalloc() for the STHYI buffer
      KVM: s390: Replace get_zeroed_page() with kzalloc() for the STSI buffer
      KVM: s390: Replace get_zeroed_page() with kzalloc() for the GIB
      KVM: s390: Replace get_zeroed_page() with kzalloc() for sie_page2 and CMMA

 arch/s390/kvm/s390/intercept.c |  9 +++++----
 arch/s390/kvm/s390/interrupt.c |  8 ++++----
 arch/s390/kvm/s390/priv.c      | 19 ++++++++++---------
 arch/s390/kvm/s390/s390.c      | 12 ++++++------
 4 files changed, 25 insertions(+), 23 deletions(-)
---
base-commit: cee9395acd8043be0644b25c34bfa86623f2b935
change-id: 20260828-s390-kvm-2015b0d777dc

--
Sincerely yours,
Mike.