[v6,00/22] KVM: Dynamically size memslot arrays

Message

Sean Christopherson Feb. 18, 2020, 9:07 p.m. UTC

The end goal of this series is to dynamically size the memslot array so
that KVM allocates memory based on the number of memslots in use, as
opposed to unconditionally allocating memory for the maximum number of
memslots.  On x86, each memslot consumes 88 bytes, and so with 2 address
spaces of 512 memslots, each VM consumes ~90k bytes for the memslots.
E.g. given a VM that uses a total of 30 memslots, dynamic sizing reduces
the memory footprint from 90k to ~2.6k bytes.

The changes required to support dynamic sizing are relatively small,
e.g. are essentially contained in patches 17 and 18.

Patches 2-16 clean up the memslot code, which has gotten quite crusty,
especially __kvm_set_memory_region().  The clean up is likely not strictly
necessary to switch to dynamic sizing, but I didn't have a remotely
reasonable level of confidence in the correctness of the dynamic sizing
without first doing the clean up.

v6:
  - Rebase to kvm/queue, 2c2787938512 ("KVM: selftests: Stop memslot ...")
  - Collect tags. [Peter]
  - Add a paragraph in the changelog for patch 16 to explain why
    kvm_arch_sync_dirty_log() is moved from s390 to generic code. [Peter]
  - Expand a comment in patch 12 to explain why a copy of the old memslot
    needs to be made in __kvm_set_memory_region() even when deleting a
    slot. [Peter]
  - Expand a comment in patch 14 to explain why @tmp is nullified after
    copying it by value. [Peter].
  - Stuff a non-canonical value into userspace_addr when deleting a
    private memslot (on x86). [Peter]
  - Use kvm_arch_flush_remote_tlbs_memslot() as the name for the new arch
    hook to flush TLB entries for a specific memslot during
    KVM_{CLEAR,GET}_DIRTY_LOG. [Peter]
  - Drop Christoffer's Acked-by and Tested-by for patch 15 due to the
    above rename.
  - Add patches 20-22 to use kvm_flush_remote_tlbs_with_address() in
    kvm_arch_flush_remote_tlbs_memslot() and consolidate existing open
    coded versions of kvm_arch_flush_remote_tlbs_memslot().

v5:
  - Make the selftest x86-only. [Christian].
  - Collect tags. [Peter]
  - Rebase to kvm/queue, fb0c5f8fb698 ("KVM: x86: inline memslot_...").

v4:
  - Add patch 01 to fix an x86 rmap/lpage bug, and patches 10 and 11 to
    resolve hidden conflicts with the bug fix.
  - Collect tags [Christian, Marc, Philippe].
  - Rebase to kvm/queue, commit e41a90be9659 ("KVM: x86/mmu: WARN if
    root_hpa is invalid when handling a page fault").
v3:
  - Fix build errors on PPC and MIPS due to missed params during
    refactoring [kbuild test robot].
  - Rename the helpers for update_memslots() and add comments describing
    the new algorithm and how it interacts with searching [Paolo].
  - Remove the unnecessary and obnoxious warning regarding memslots being
    a flexible array [Paolo].
  - Fix typos in the changelog of patch 09/15 [Christoffer].
  - Collect tags [Christoffer].

v2:
  - Split "Drop kvm_arch_create_memslot()" into three patches to move
    minor functional changes to standalone patches [Janosch].
  - Rebase to latest kvm/queue (f0574a1cea5b, "KVM: x86: fix ...")
  - Collect an Acked-by and a Reviewed-by

Sean Christopherson (22):
  KVM: x86: Allocate new rmap and large page tracking when moving
    memslot
  KVM: Reinstall old memslots if arch preparation fails
  KVM: Don't free new memslot if allocation of said memslot fails
  KVM: PPC: Move memslot memory allocation into prepare_memory_region()
  KVM: x86: Allocate memslot resources during prepare_memory_region()
  KVM: Drop kvm_arch_create_memslot()
  KVM: Explicitly free allocated-but-unused dirty bitmap
  KVM: Refactor error handling for setting memory region
  KVM: Move setting of memslot into helper routine
  KVM: Drop "const" attribute from old memslot in commit_memory_region()
  KVM: x86: Free arrays for old memslot when moving memslot's base gfn
  KVM: Move memslot deletion to helper function
  KVM: Simplify kvm_free_memslot() and all its descendents
  KVM: Clean up local variable usage in __kvm_set_memory_region()
  KVM: Provide common implementation for generic dirty log functions
  KVM: Ensure validity of memslot with respect to kvm_get_dirty_log()
  KVM: Terminate memslot walks via used_slots
  KVM: Dynamically size memslot array based on number of used slots
  KVM: selftests: Add test for KVM_SET_USER_MEMORY_REGION
  KVM: x86/mmu: Move kvm_arch_flush_remote_tlbs_memslot() to mmu.c
  KVM: x86/mmu: Use ranged-based TLB flush for dirty log memslot flush
  KVM: x86/mmu: Consolidate open coded variants of memslot TLB flushes

 arch/mips/include/asm/kvm_host.h              |   2 +-
 arch/mips/kvm/mips.c                          |  71 +-
 arch/powerpc/include/asm/kvm_ppc.h            |  17 +-
 arch/powerpc/kvm/book3s.c                     |  22 +-
 arch/powerpc/kvm/book3s_hv.c                  |  36 +-
 arch/powerpc/kvm/book3s_pr.c                  |  20 +-
 arch/powerpc/kvm/booke.c                      |  17 +-
 arch/powerpc/kvm/powerpc.c                    |  15 +-
 arch/s390/include/asm/kvm_host.h              |   2 +-
 arch/s390/kvm/kvm-s390.c                      |  23 +-
 arch/x86/include/asm/kvm_page_track.h         |   3 +-
 arch/x86/kvm/mmu/mmu.c                        |  42 +-
 arch/x86/kvm/mmu/page_track.c                 |  15 +-
 arch/x86/kvm/x86.c                            | 120 +---
 include/linux/kvm_host.h                      |  48 +-
 tools/testing/selftests/kvm/.gitignore        |   1 +
 tools/testing/selftests/kvm/Makefile          |   1 +
 .../testing/selftests/kvm/include/kvm_util.h  |   1 +
 tools/testing/selftests/kvm/lib/kvm_util.c    |  30 +
 .../kvm/x86_64/set_memory_region_test.c       | 142 ++++
 virt/kvm/arm/arm.c                            |  48 +-
 virt/kvm/arm/mmu.c                            |  20 +-
 virt/kvm/kvm_main.c                           | 624 ++++++++++++------
 23 files changed, 754 insertions(+), 566 deletions(-)
 create mode 100644 tools/testing/selftests/kvm/x86_64/set_memory_region_test.c