[PATCH 00/13] KVM: Dynamically size memslot arrays

Sean Christopherson
2019-09-11T18:50:45Z

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 12/13 and 13/13. Patches 1-11
clean up the memslot code, which has gotten quite crusy, 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.

Testing, especially non-x86 platforms, would be greatly appreciated. I'd
really like to get at least one Tested-by from all architectures. The
non-x86 changes are for all intents and purposes untested, e.g. I compile
tested pieces of the code by copying them into x86, but that's it. In
theory, the vast majority of the functional changes are arch agnostic, in
theory...

Sean Christopherson (13):
KVM: Reinstall old memslots if arch preparation 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: Refactor error handling for setting memory region
KVM: Move setting of memslot into helper routine
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

arch/mips/include/asm/kvm_host.h | 2 +-
arch/mips/kvm/mips.c | 68 +---
arch/powerpc/include/asm/kvm_ppc.h | 14 +-
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 | 13 +-
arch/s390/include/asm/kvm_host.h | 2 +-
arch/s390/kvm/kvm-s390.c | 21 +-
arch/x86/include/asm/kvm_page_track.h | 3 +-
arch/x86/kvm/page_track.c | 15 +-
arch/x86/kvm/x86.c | 100 ++---
include/linux/kvm_host.h | 48 +--
virt/kvm/arm/arm.c | 47 +--
virt/kvm/arm/mmu.c | 18 +-
virt/kvm/kvm_main.c | 546 ++++++++++++++++----------
17 files changed, 467 insertions(+), 525 deletions(-)

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2.22.0