[PATCH v6 00/28] KVM: s390: gmap rewrite, the real deal

Claudio Imbrenda
2025-12-22T16:50:41Z

This series is the last big series of the gmap rewrite. It introduces
the new code and actually uses it. The old code is then removed.

KVM on s390 will now use the mmu_notifier, like most other
architectures. The gmap address space is now completely separate from
userspace; no level of the page tables is shared between guest mapping
and userspace.

One of the biggest advantages is that the page size of userspace is
completely independent of the page size used by the guest. Userspace
can mix normal pages, THPs, hugetlbfs, and more.

It's now possible to have nested guests and guests with huge pages
running on the same host. In fact, it's possible to have a nested
guest on a guest with huge pages. Transparent hugepages are also
possible.

Patches 1 to 11 are mostly preparations; introducing some new bits and
functions, and moving code around.

Patches 12 to 21 are the meat of the new gmap code; page table management
functions and gmap management. This is the code that will be used to
manage guest memory.

Patch 24 is unfortunately big; the existing code is converted to use
the new gmap and all references to the old gmap are removed. This needs
to be done all at once, unfortunately, hence the size of the patch.

Patch 25 and 26 remove all the now unused code.

Patch 27 and 28 allow for 1M pages to be used to back guests, and add
some more functions that are useful for testing.

v5->v6:
* Added a mutex to avoid races during import-like operations in
protected guests
* The functions uv_convert_from_secure_folio() and uv_destroy_folio()
now work on the whole folio, and not just its first page
* Added warnings if uv_convert_from_secure_pte() fails in ptep_*()
* Changed the way shadow gmaps do reference counting
* Use a bitmap for gmap flags, instead of individual bool variables
* Rework the make_secure logic to work on gmap only, and not on
userspace addresses
* Some refactorings
* Rebased onto 6.19-rc2
* Added more comments
* Minor style fixes

v4->v5:
* fix some locking issues
* fix comments and documentation

v3->v4:
* dat_link() can now return -ENOMEM when appropriate
* fixed a few vSIE races that led to use-after-free or deadlocks
* split part of the previous patch 23 and move it after patch 17, merge
the rest of the patch into patch 19
* fix -ENOMEM handling in handle_pfmf() and handle_sske()

v2->v3:
* Add lots of small comments and cosmetic fixes
* Rename some functions to improve clarity
* Remove unused helper functions and macros
* Rename inline asm constraints labels to make them more understandable
* Refactor the code to pre-allocate the page tables (using custom
caches) when sleeping is allowed, use the cached pages when holding
spinlocks and handle gracefully allocation failures (i.e. retry
instead of killing the guest)
* Refactor the code for fault handling; it's now in a separate file,
and it takes a callback that can be optionally called when all the
relevant locks are still held
* Use assembler mnemonics instead of manually specifying the opcode
where appropriate
* Remove the LEVEL_* enum, and use TABLE_TYPE_* macros instead;
introduce new TABLE_TYPE_PAGE_TABLE
* Remove usage of cpu_has_idte() since it is being removed from the
kernel
* Improve storage key handling and PGSTE locking
* Introduce struct guest_fault to represent the state of a guest fault
that is being resolved
* Minor CMMA fixes

Claudio Imbrenda (28):
KVM: s390: Refactor pgste lock and unlock functions
KVM: s390: add P bit in table entry bitfields, move union vaddress
s390: Make UV folio operations work on whole folio
s390: Move sske_frame() to a header
KVM: s390: Add gmap_helper_set_unused()
KVM: s390: Introduce import_lock
KVM: s390: Export two functions
s390/mm: Warn if uv_convert_from_secure_pte() fails
KVM: s390: vsie: Pass gmap explicitly as parameter
KVM: s390: Enable KVM_GENERIC_MMU_NOTIFIER
KVM: s390: Rename some functions in gaccess.c
KVM: s390: KVM-specific bitfields and helper functions
KVM: s390: KVM page table management functions: allocation
KVM: s390: KVM page table management functions: clear and replace
KVM: s390: KVM page table management functions: walks
KVM: s390: KVM page table management functions: storage keys
KVM: s390: KVM page table management functions: lifecycle management
KVM: s390: KVM page table management functions: CMMA
KVM: s390: New gmap code
KVM: s390: Add helper functions for fault handling
KVM: s390: Add some helper functions needed for vSIE
KVM: s390: Stop using CONFIG_PGSTE
KVM: s390: Storage key functions refactoring
KVM: s390: Switch to new gmap
KVM: s390: Remove gmap from s390/mm
KVM: S390: Remove PGSTE code from linux/s390 mm
KVM: s390: Enable 1M pages for gmap
KVM: s390: Storage key manipulation IOCTL

MAINTAINERS | 2 -
arch/s390/Kconfig | 3 -
arch/s390/include/asm/dat-bits.h | 32 +-
arch/s390/include/asm/gmap.h | 174 --
arch/s390/include/asm/gmap_helpers.h | 1 +
arch/s390/include/asm/hugetlb.h | 6 -
arch/s390/include/asm/kvm_host.h | 7 +
arch/s390/include/asm/mmu.h | 13 -
arch/s390/include/asm/mmu_context.h | 6 +-
arch/s390/include/asm/page.h | 4 -
arch/s390/include/asm/pgalloc.h | 4 -
arch/s390/include/asm/pgtable.h | 171 +-
arch/s390/include/asm/tlb.h | 3 -
arch/s390/include/asm/uaccess.h | 70 +-
arch/s390/include/asm/uv.h | 3 +-
arch/s390/kernel/uv.c | 142 +-
arch/s390/kvm/Kconfig | 2 +
arch/s390/kvm/Makefile | 3 +-
arch/s390/kvm/dat.c | 1368 +++++++++++++++
arch/s390/kvm/dat.h | 965 ++++++++++
arch/s390/kvm/diag.c | 2 +-
arch/s390/kvm/faultin.c | 148 ++
arch/s390/kvm/faultin.h | 92 +
arch/s390/kvm/gaccess.c | 940 +++++-----
arch/s390/kvm/gaccess.h | 20 +-
arch/s390/kvm/gmap-vsie.c | 141 --
arch/s390/kvm/gmap.c | 1151 ++++++++++++
arch/s390/kvm/gmap.h | 240 +++
arch/s390/kvm/intercept.c | 15 +-
arch/s390/kvm/interrupt.c | 6 +-
arch/s390/kvm/kvm-s390.c | 939 ++++------
arch/s390/kvm/kvm-s390.h | 27 +-
arch/s390/kvm/priv.c | 213 +--
arch/s390/kvm/pv.c | 177 +-
arch/s390/kvm/vsie.c | 193 +-
arch/s390/lib/uaccess.c | 184 +-
arch/s390/mm/Makefile | 1 -
arch/s390/mm/fault.c | 4 +-
arch/s390/mm/gmap.c | 2436 --------------------------
arch/s390/mm/gmap_helpers.c | 96 +-
arch/s390/mm/hugetlbpage.c | 24 -
arch/s390/mm/page-states.c | 1 +
arch/s390/mm/pageattr.c | 7 -
arch/s390/mm/pgalloc.c | 24 -
arch/s390/mm/pgtable.c | 814 +--------
include/uapi/linux/kvm.h | 10 +
mm/khugepaged.c | 9 -
47 files changed, 5415 insertions(+), 5478 deletions(-)
delete mode 100644 arch/s390/include/asm/gmap.h
create mode 100644 arch/s390/kvm/dat.c
create mode 100644 arch/s390/kvm/dat.h
create mode 100644 arch/s390/kvm/faultin.c
create mode 100644 arch/s390/kvm/faultin.h
delete mode 100644 arch/s390/kvm/gmap-vsie.c
create mode 100644 arch/s390/kvm/gmap.c
create mode 100644 arch/s390/kvm/gmap.h
delete mode 100644 arch/s390/mm/gmap.c

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2.52.0