| Message ID | 20240724011037.3671523-10-jthoughton@google.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm: multi-gen LRU: Walk secondary MMU page tables while aging | expand |
On 2024-07-24 01:10 AM, James Houghton wrote: > These fast-only versions simply ignore the shadow MMU. We can locklessly > handle the shadow MMU later. > > Set HAVE_KVM_MMU_NOTIFIER_YOUNG_FAST_ONLY for X86_64 only, as that is > the only case where the TDP MMU might be used. Without the TDP MMU, the > fast-only notifiers will always be no-ops. It would be ideal not to > report has_fast_only if !tdp_mmu_enabled, but tdp_mmu_enabled can be > changed at any time. tdp_mmu_enabled is a read-only KVM parameter. And even when it was writable, it was still fixed for a given VM at VM creation time. Would it make more sense to have kvm_arch_post_init_vm() set has_fast_aging if the architecture supports it. And for x86 that means iff tdp_mmu_enabled. > > Signed-off-by: James Houghton <jthoughton@google.com> > --- > arch/x86/kvm/Kconfig | 1 + > arch/x86/kvm/mmu/mmu.c | 4 ++-- > 2 files changed, 3 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig > index 6ac43074c5e9..ed9049cf1255 100644 > --- a/arch/x86/kvm/Kconfig > +++ b/arch/x86/kvm/Kconfig > @@ -24,6 +24,7 @@ config KVM > select KVM_COMMON > select KVM_GENERIC_MMU_NOTIFIER > select KVM_MMU_NOTIFIER_YOUNG_LOCKLESS > + select HAVE_KVM_MMU_NOTIFIER_YOUNG_FAST_ONLY if X86_64 > select HAVE_KVM_IRQCHIP > select HAVE_KVM_PFNCACHE > select HAVE_KVM_DIRTY_RING_TSO > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > index 919d59385f89..3c6c9442434a 100644 > --- a/arch/x86/kvm/mmu/mmu.c > +++ b/arch/x86/kvm/mmu/mmu.c > @@ -1641,7 +1641,7 @@ bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) > if (tdp_mmu_enabled) > young |= kvm_tdp_mmu_age_gfn_range(kvm, range); > > - if (kvm_has_shadow_mmu_sptes(kvm)) { > + if (!range->arg.fast_only && kvm_has_shadow_mmu_sptes(kvm)) { > write_lock(&kvm->mmu_lock); > young = kvm_handle_gfn_range(kvm, range, kvm_age_rmap); > write_unlock(&kvm->mmu_lock); > @@ -1657,7 +1657,7 @@ bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) > if (tdp_mmu_enabled) > young |= kvm_tdp_mmu_test_age_gfn(kvm, range); > > - if (!young && kvm_has_shadow_mmu_sptes(kvm)) { > + if (!young && !range->arg.fast_only && kvm_has_shadow_mmu_sptes(kvm)) { > write_lock(&kvm->mmu_lock); > young = kvm_handle_gfn_range(kvm, range, kvm_test_age_rmap); > write_unlock(&kvm->mmu_lock); > -- > 2.46.0.rc1.232.g9752f9e123-goog >
diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig index 6ac43074c5e9..ed9049cf1255 100644 --- a/arch/x86/kvm/Kconfig +++ b/arch/x86/kvm/Kconfig @@ -24,6 +24,7 @@ config KVM select KVM_COMMON select KVM_GENERIC_MMU_NOTIFIER select KVM_MMU_NOTIFIER_YOUNG_LOCKLESS + select HAVE_KVM_MMU_NOTIFIER_YOUNG_FAST_ONLY if X86_64 select HAVE_KVM_IRQCHIP select HAVE_KVM_PFNCACHE select HAVE_KVM_DIRTY_RING_TSO diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 919d59385f89..3c6c9442434a 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -1641,7 +1641,7 @@ bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) if (tdp_mmu_enabled) young |= kvm_tdp_mmu_age_gfn_range(kvm, range); - if (kvm_has_shadow_mmu_sptes(kvm)) { + if (!range->arg.fast_only && kvm_has_shadow_mmu_sptes(kvm)) { write_lock(&kvm->mmu_lock); young = kvm_handle_gfn_range(kvm, range, kvm_age_rmap); write_unlock(&kvm->mmu_lock); @@ -1657,7 +1657,7 @@ bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range) if (tdp_mmu_enabled) young |= kvm_tdp_mmu_test_age_gfn(kvm, range); - if (!young && kvm_has_shadow_mmu_sptes(kvm)) { + if (!young && !range->arg.fast_only && kvm_has_shadow_mmu_sptes(kvm)) { write_lock(&kvm->mmu_lock); young = kvm_handle_gfn_range(kvm, range, kvm_test_age_rmap); write_unlock(&kvm->mmu_lock);
These fast-only versions simply ignore the shadow MMU. We can locklessly handle the shadow MMU later. Set HAVE_KVM_MMU_NOTIFIER_YOUNG_FAST_ONLY for X86_64 only, as that is the only case where the TDP MMU might be used. Without the TDP MMU, the fast-only notifiers will always be no-ops. It would be ideal not to report has_fast_only if !tdp_mmu_enabled, but tdp_mmu_enabled can be changed at any time. Signed-off-by: James Houghton <jthoughton@google.com> --- arch/x86/kvm/Kconfig | 1 + arch/x86/kvm/mmu/mmu.c | 4 ++-- 2 files changed, 3 insertions(+), 2 deletions(-)