On 2019-12-17 20:40, Sean Christopherson wrote:
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 17/19 and 18/19.
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.
The only functional change in v4 is the addition of an x86-specific
bug
fix in x86's handling of KVM_MR_MOVE. The bug fix is not directly
related
to dynamically allocating memslots, but it has subtle and hidden
conflicts
with the cleanup patches, and the fix is higher priority than
anything
else in the series, i.e. should be merged first.
On non-x86 architectures, v3 and v4 should be functionally
equivalent,
the only non-x86 change in v4 is the dropping of a "const" in
kvm_arch_commit_memory_region().
Gave it another go on top of 5.5-rc2 on an arm64 box, and nothing
exploded. So thumbs up from me.
Thanks,
M.
--
Jazz is not dead. It just smells funny...
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