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Subject[PATCH 00/15] Currently disabling dirty logging with the TDP MMU is extremely slow. On a 96 vCPU / 96G VM it takes ~45 seconds to disable dirty logging with the TDP MMU, as opposed to ~3.5 seconds with the legacy MMU. This series optimizes TLB flushes an
From
Testing:
Ran KVM selftests and kvm-unit-tests on an Intel Skylake. This
series introduced no new failures.

Performance:
To collect these results I needed to apply Mingwei's patch
"selftests: KVM: align guest physical memory base address to 1GB"
https://lkml.org/lkml/2021/8/29/310
David Matlack is going to send out an updated version of that patch soon.

Without this series, TDP MMU:
> ./dirty_log_perf_test -v 96 -s anonymous_hugetlb_1gb
Test iterations: 2
Testing guest mode: PA-bits:ANY, VA-bits:48, 4K pages
guest physical test memory offset: 0x3fe7c0000000
Populate memory time: 10.966500447s
Enabling dirty logging time: 0.002068737s

Iteration 1 dirty memory time: 0.047556280s
Iteration 1 get dirty log time: 0.001253914s
Iteration 1 clear dirty log time: 0.049716661s
Iteration 2 dirty memory time: 3.679662016s
Iteration 2 get dirty log time: 0.000659546s
Iteration 2 clear dirty log time: 1.834329322s
Disabling dirty logging time: 45.738439510s
Get dirty log over 2 iterations took 0.001913460s. (Avg 0.000956730s/iteration)
Clear dirty log over 2 iterations took 1.884045983s. (Avg 0.942022991s/iteration)

Without this series, Legacy MMU:
> ./dirty_log_perf_test -v 96 -s anonymous_hugetlb_1gb
Test iterations: 2
Testing guest mode: PA-bits:ANY, VA-bits:48, 4K pages
guest physical test memory offset: 0x3fe7c0000000
Populate memory time: 12.664750666s
Enabling dirty logging time: 0.002025510s

Iteration 1 dirty memory time: 0.046240875s
Iteration 1 get dirty log time: 0.001864342s
Iteration 1 clear dirty log time: 0.170243637s
Iteration 2 dirty memory time: 31.571088701s
Iteration 2 get dirty log time: 0.000626245s
Iteration 2 clear dirty log time: 1.294817729s
Disabling dirty logging time: 3.566831573s
Get dirty log over 2 iterations took 0.002490587s. (Avg 0.001245293s/iteration)
Clear dirty log over 2 iterations took 1.465061366s. (Avg 0.732530683s/iteration)

With this series, TDP MMU:
(Updated since RFC. Pulling out patches 1-4 could have a performance impact.)
> ./dirty_log_perf_test -v 96 -s anonymous_hugetlb_1gb
Test iterations: 2
Testing guest mode: PA-bits:ANY, VA-bits:48, 4K pages
guest physical test memory offset: 0x3fe7c0000000
Populate memory time: 12.225242366s
Enabling dirty logging time: 0.002063442s

Iteration 1 dirty memory time: 0.047598123s
Iteration 1 get dirty log time: 0.001247702s
Iteration 1 clear dirty log time: 0.051062420s
Iteration 2 dirty memory time: 3.660439803s
Iteration 2 get dirty log time: 0.000736229s
Iteration 2 clear dirty log time: 1.043469951s
Disabling dirty logging time: 1.400549627s
Get dirty log over 2 iterations took 0.001983931s. (Avg 0.000991965s/iteration)
Clear dirty log over 2 iterations took 1.094532371s. (Avg 0.547266185s/iteration)

Patch breakdown:
Patches 1 eliminates extra TLB flushes while disabling dirty logging.
Patches 2-8 remove the need for a vCPU pointer to make_spte
Patches 9-14 are small refactors in perparation for patch 19
Patch 15 implements in-place largepage promotion when disabling dirty logging

Changelog:
RFC -> v1:
Dropped the first 4 patches from the series. Patch 1 was sent
separately, patches 2-4 will be taken over by Sean Christopherson.
Incorporated David Matlack's Reviewed-by.

Ben Gardon (15):
KVM: x86/mmu: Remove redundant flushes when disabling dirty logging
KVM: x86/mmu: Introduce vcpu_make_spte
KVM: x86/mmu: Factor wrprot for nested PML out of make_spte
KVM: x86/mmu: Factor mt_mask out of make_spte
KVM: x86/mmu: Remove need for a vcpu from
kvm_slot_page_track_is_active
KVM: x86/mmu: Remove need for a vcpu from mmu_try_to_unsync_pages
KVM: x86/mmu: Factor shadow_zero_check out of make_spte
KVM: x86/mmu: Replace vcpu argument with kvm pointer in make_spte
KVM: x86/mmu: Factor out the meat of reset_tdp_shadow_zero_bits_mask
KVM: x86/mmu: Propagate memslot const qualifier
KVM: x86/MMU: Refactor vmx_get_mt_mask
KVM: x86/mmu: Factor out part of vmx_get_mt_mask which does not depend
on vcpu
KVM: x86/mmu: Add try_get_mt_mask to x86_ops
KVM: x86/mmu: Make kvm_is_mmio_pfn usable outside of spte.c
KVM: x86/mmu: Promote pages in-place when disabling dirty logging

arch/x86/include/asm/kvm-x86-ops.h | 1 +
arch/x86/include/asm/kvm_host.h | 2 +
arch/x86/include/asm/kvm_page_track.h | 6 +-
arch/x86/kvm/mmu/mmu.c | 45 +++++++------
arch/x86/kvm/mmu/mmu_internal.h | 6 +-
arch/x86/kvm/mmu/page_track.c | 8 +--
arch/x86/kvm/mmu/paging_tmpl.h | 6 +-
arch/x86/kvm/mmu/spte.c | 43 ++++++++----
arch/x86/kvm/mmu/spte.h | 17 +++--
arch/x86/kvm/mmu/tdp_mmu.c | 97 +++++++++++++++++++++------
arch/x86/kvm/mmu/tdp_mmu.h | 5 +-
arch/x86/kvm/svm/svm.c | 8 +++
arch/x86/kvm/vmx/vmx.c | 40 ++++++-----
include/linux/kvm_host.h | 10 +--
virt/kvm/kvm_main.c | 12 ++--
15 files changed, 205 insertions(+), 101 deletions(-)

--
2.34.0.rc1.387.gb447b232ab-goog

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