Re: [PATCH v3 00/15] KVM: Dynamically size memslot arrays

From: Christoffer Dall
Date: Fri Oct 25 2019 - 09:28:05 EST

On Thu, Oct 24, 2019 at 04:07:29PM -0700, 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 14/15 and 15/15. Patches 1-13
> 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.
> Christoffer, I added your Tested-by to the patches that I was confident
> would be fully tested based on the desription of what you tested. Let me
> know if you disagree with any of 'em.
The only testing I've done of patch 9 would be via the vm_free part of
kvm selftest, so not sure how valid that is, but sure.

Looks fine otherwise.