KVM: x86/MMU: Zap non-leaf SPTEs when disabling dirty logging

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Currently disabling dirty logging with the TDP MMU is extremely slow.
On a 96 vCPU / 96G VM backed with gigabyte pages, it takes ~200 seconds
to disable dirty logging with the TDP MMU, as opposed to ~4 seconds with
the shadow MMU.

When disabling dirty logging, zap non-leaf parent entries to allow
replacement with huge pages instead of recursing and zapping all of the
child, leaf entries. This reduces the number of TLB flushes required.
and reduces the disable dirty log time with the TDP MMU to ~3 seconds.

Opportunistically add a WARN() to catch GFNs that are mapped at a
higher level than their max level.

Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20220525230904.1584480-1-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

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Ben Gardon 2022-05-25 23:09:04 +00:00 • committed by Paolo Bonzini

parent 1df931d95f

commit 5ba7c4c6d1

3 changed files with 42 additions and 6 deletions

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9

arch/x86/kvm/mmu/tdp_iter.c

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1

arch/x86/kvm/mmu/tdp_iter.h

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38

arch/x86/kvm/mmu/tdp_mmu.c

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