This series refines mmu zap caused by EPT memory type update when guest
MTRRs are honored.
The first 5 patches revolve around utilizing helper functions to check if
KVM TDP honors guest MTRRs, so that TDP zap and page fault max_level
reduction are only targeted to TDPs that honor guest MTRRs.
-The 5th patch will trigger zapping of TDP leaf entries if non-coherent
DMA devices count goes from 0 to 1 or from 1 to 0.
The last 6 patches are fixes and optimizations for mmu zaps happen when
guest MTRRs are honored. Those mmu zaps are usually triggered from all
vCPUs in bursts on all GFN ranges, intending to remove stale memtypes of
TDP entries.
- The 6th patch places TDP zap to when CR0.CD toggles and when guest MTRRs
update under CR0.CD=0.
- The 7th-8th patches refine KVM_X86_QUIRK_CD_NW_CLEARED by removing the
IPAT bit in EPT memtype when CR0.CD=1 and guest MTRRs are honored.
- The 9th-11th patches are optimizations of the mmu zap when guest MTRRs
are honored by serializing vCPUs' gfn zap requests and calculating of
precise fine-grained ranges to zap.
They are put in mtrr.c because the optimizations are related to when
guest MTRRs are honored and because it requires to read guest MTRRs
for fine-grained ranges.
Calls to kvm_unmap_gfn_range() are not included into the optimization,
because they are not triggered from all vCPUs in bursts and not all of
them are blockable. They usually happen at memslot removal and thus do
not affect the mmu zaps when guest MTRRs are honored. Also, current
performance data shows that there's no observable performance difference
to mmu zaps by turning on/off auto numa balancing triggered
kvm_unmap_gfn_range().
A reference performance data for last 6 patches as below:
Base: base code before patch 6
C6-8: includes base code + patches 6 + 7 + 8
patch 6: move TDP zaps from guest MTRRs update to CR0.CD toggling
patch 7: drop IPAT in memtype when CD=1 for
KVM_X86_QUIRK_CD_NW_CLEARED
patch 8: move vmx code to get EPT memtype when CR0.CD=1 to x86 common
code
C9: includes C6-8 + patch 9
patch 9: serialize vCPUs to zap gfn when guest MTRRs are honored
C10: includes C9 + patch 10
patch 10: fine-grained gfn zap when guest MTRRs are honored
C11: includes C10 + patch 11
patch 11: split a single gfn zap range when guest MTRRs are honored
vCPUs cnt: 8, guest memory: 16G
Physical CPU frequency: 3100 MHz
| OVMF | Seabios |
| EPT zap cycles | EPT zap cnt | EPT zap cycles | EPT zap cnt |
Base | 3444.97M | 84 | 61.29M | 50 |
C6-8 | 4343.68M | 74 | 503.04M | 42 |*
C9 | 261.45M | 74 | 106.64M | 42 |
C10 | 157.42M | 74 | 71.04M | 42 |
C11 | 33.95M | 74 | 24.04M | 42 |
* With C8, EPT zap cnt are reduced because there are some MTRR updates
under CR0.CD=1.
EPT zap cycles increases a bit (especially true in case of Seabios)
because concurrency is more intense when CR0.CD toggles than when
guest MTRRs update.
(patch 7/8 are neglectable in performance)
Changelog:
v2 --> v3:
1. Updated patch 1 about definition of honor guest MTRRs helper. (Sean)
2. Added patch 2 to use honor guest MTRRs helper in kvm_tdp_page_fault().
(Sean)
3. Remove unnecessary calculation of MTRR ranges.
(Chao Gao, Kai Huang, Sean)
4. Updated patches 3-5 to use the helper. (Chao Gao, Kai Huang, Sean)
5. Added patches 6,7 to reposition TDP zap and drop IPAT bit. (Sean)
6. Added patch 8 to prepare for patch 10's memtype calculation when
CR0.CD=1.
7. Added patches 9-11 to speed up MTRR update /CD0 toggle when guest
MTRRs are honored. (Sean)
8. Dropped per-VM based MTRRs in v2 (Sean)
v1 --> v2:
1. Added a helper to skip non EPT case in patch 1
2. Added patch 2 to skip mmu zap when guest CR0_CD changes if EPT is not
enabled. (Chao Gao)
3. Added patch 3 to skip mmu zap when guest MTRR changes if EPT is not
enabled.
4. Do not mention TDX in patch 4 as the code is not merged yet (Chao Gao)
5. Added patches 5-6 to reduce EPT zap during guest bootup.
v2:
https://lore.kernel.org/all/20230509134825.1523-1-yan.y.zhao@xxxxxxxxx/
v1:
https://lore.kernel.org/all/20230508034700.7686-1-yan.y.zhao@xxxxxxxxx/
Yan Zhao (11):
KVM: x86/mmu: helpers to return if KVM honors guest MTRRs
KVM: x86/mmu: Use KVM honors guest MTRRs helper in
kvm_tdp_page_fault()
KVM: x86/mmu: Use KVM honors guest MTRRs helper when CR0.CD toggles
KVM: x86/mmu: Use KVM honors guest MTRRs helper when update mtrr
KVM: x86/mmu: zap KVM TDP when noncoherent DMA assignment starts/stops
KVM: x86/mmu: move TDP zaps from guest MTRRs update to CR0.CD toggling
KVM: VMX: drop IPAT in memtype when CD=1 for
KVM_X86_QUIRK_CD_NW_CLEARED
KVM: x86: move vmx code to get EPT memtype when CR0.CD=1 to x86 common
code
KVM: x86/mmu: serialize vCPUs to zap gfn when guest MTRRs are honored
KVM: x86/mmu: fine-grained gfn zap when guest MTRRs are honored
KVM: x86/mmu: split a single gfn zap range when guest MTRRs are
honored
arch/x86/include/asm/kvm_host.h | 4 +
arch/x86/kvm/mmu.h | 7 +
arch/x86/kvm/mmu/mmu.c | 18 +-
arch/x86/kvm/mtrr.c | 286 +++++++++++++++++++++++++++++++-
arch/x86/kvm/vmx/vmx.c | 11 +-
arch/x86/kvm/x86.c | 25 ++-
arch/x86/kvm/x86.h | 2 +
7 files changed, 333 insertions(+), 20 deletions(-)
base-commit: 24ff4c08e5bbdd7399d45f940f10fed030dfadda
--
2.17.1
