[v4,0/2] KVM: x86/mmu: Skip mmu_notifier changes when possible

Message

David Stevens Feb. 22, 2021, 2:45 a.m. UTC

These patches reduce how often mmu_notifier updates block guest page
faults. The primary benefit of this is the reduction in the likelihood
of extreme latency when handling a page fault due to another thread
having been preempted while modifying host virtual addresses.

v3 -> v4:
 - Fix bug by skipping prefetch during invalidation

v2 -> v3:
 - Added patch to skip check for MMIO page faults
 - Style changes

David Stevens (1):
  KVM: x86/mmu: Consider the hva in mmu_notifier retry

Sean Christopherson (1):
  KVM: x86/mmu: Skip mmu_notifier check when handling MMIO page fault

 arch/powerpc/kvm/book3s_64_mmu_hv.c    |  2 +-
 arch/powerpc/kvm/book3s_64_mmu_radix.c |  2 +-
 arch/x86/kvm/mmu/mmu.c                 | 23 ++++++++++++++------
 arch/x86/kvm/mmu/paging_tmpl.h         |  7 ++++---
 include/linux/kvm_host.h               | 25 +++++++++++++++++++++-
 virt/kvm/kvm_main.c                    | 29 ++++++++++++++++++++++----
 6 files changed, 72 insertions(+), 16 deletions(-)

Comments

Paolo Bonzini Feb. 22, 2021, 6:17 p.m. UTC | #1

On 22/02/21 03:45, David Stevens wrote:
> These patches reduce how often mmu_notifier updates block guest page
> faults. The primary benefit of this is the reduction in the likelihood
> of extreme latency when handling a page fault due to another thread
> having been preempted while modifying host virtual addresses.
> 
> v3 -> v4:
>   - Fix bug by skipping prefetch during invalidation
> 
> v2 -> v3:
>   - Added patch to skip check for MMIO page faults
>   - Style changes
> 
> David Stevens (1):
>    KVM: x86/mmu: Consider the hva in mmu_notifier retry
> 
> Sean Christopherson (1):
>    KVM: x86/mmu: Skip mmu_notifier check when handling MMIO page fault
> 
>   arch/powerpc/kvm/book3s_64_mmu_hv.c    |  2 +-
>   arch/powerpc/kvm/book3s_64_mmu_radix.c |  2 +-
>   arch/x86/kvm/mmu/mmu.c                 | 23 ++++++++++++++------
>   arch/x86/kvm/mmu/paging_tmpl.h         |  7 ++++---
>   include/linux/kvm_host.h               | 25 +++++++++++++++++++++-
>   virt/kvm/kvm_main.c                    | 29 ++++++++++++++++++++++----
>   6 files changed, 72 insertions(+), 16 deletions(-)
> 

Rebased, and queued with the fix that Sean suggested.

Paolo