[PATCH v3 00/23] KVM: s390: gmap rewrite, the real deal

Claudio Imbrenda
2025-11-06T16:11:25Z

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.

The insertions/deletions balance is negative both for this series, and
for the whole rewrite, also considering all the preparatory patches.

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.

Patches 1 to 6 are mostly preparations; introducing some new bits and
functions, and moving code around.

Patch 7 to 16 is 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 18 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 19 and 20 remove all the now unused code.

Patch 21 and 22 allow for 1M pages to be used to back guests, and add
some more functions that are useful for testing.

Patch 23 fixes storage key manipulation functions, which would
otherwise be broken by the new code.

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 (23):
KVM: s390: Refactor pgste lock and unlock functions
KVM: s390: add P bit in table entry bitfields, move union vaddress
s390: Move sske_frame() to a header
KVM: s390: Add gmap_helper_set_unused()
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: 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
KVM: s390: Fix storage key memop IOCTLs

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/kvm_host.h | 5 +
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 | 163 +-
arch/s390/include/asm/tlb.h | 3 -
arch/s390/include/asm/uaccess.h | 70 +-
arch/s390/kvm/Kconfig | 3 +-
arch/s390/kvm/Makefile | 3 +-
arch/s390/kvm/dat.c | 1362 ++++++++++++++
arch/s390/kvm/dat.h | 971 ++++++++++
arch/s390/kvm/diag.c | 2 +-
arch/s390/kvm/faultin.c | 148 ++
arch/s390/kvm/faultin.h | 92 +
arch/s390/kvm/gaccess.c | 929 +++++-----
arch/s390/kvm/gaccess.h | 20 +-
arch/s390/kvm/gmap-vsie.c | 141 --
arch/s390/kvm/gmap.c | 1125 ++++++++++++
arch/s390/kvm/gmap.h | 159 ++
arch/s390/kvm/intercept.c | 15 +-
arch/s390/kvm/interrupt.c | 2 +-
arch/s390/kvm/kvm-s390.c | 926 ++++------
arch/s390/kvm/kvm-s390.h | 28 +-
arch/s390/kvm/priv.c | 207 +--
arch/s390/kvm/pv.c | 67 +-
arch/s390/kvm/vsie.c | 117 +-
arch/s390/lib/uaccess.c | 184 +-
arch/s390/mm/Makefile | 1 -
arch/s390/mm/fault.c | 4 +-
arch/s390/mm/gmap.c | 2453 --------------------------
arch/s390/mm/gmap_helpers.c | 87 +-
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 | 818 +--------
include/uapi/linux/kvm.h | 10 +
mm/khugepaged.c | 9 -
44 files changed, 5116 insertions(+), 5303 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

--
2.51.1