diff options
| author | James Houghton <jthoughton@google.com> | 2025-02-04 00:40:29 +0000 |
|---|---|---|
| committer | Sean Christopherson <seanjc@google.com> | 2025-02-14 07:16:35 -0800 |
| commit | aa34b811650ce87a82d1bff027eeb15e2856f7bb (patch) | |
| tree | 726f5e1cfeac59a9b3c042e079a1709dc4f90ccd /virt | |
| parent | 374ccd63600bc98453e7ab33fd457b57f6faacbc (diff) | |
KVM: Allow lockless walk of SPTEs when handing aging mmu_notifier event
It is possible to correctly do aging without taking the KVM MMU lock,
or while taking it for read; add a Kconfig to let architectures do so.
Architectures that select KVM_MMU_LOCKLESS_AGING are responsible for
correctness.
Suggested-by: Yu Zhao <yuzhao@google.com>
Signed-off-by: James Houghton <jthoughton@google.com>
Reviewed-by: David Matlack <dmatlack@google.com>
Link: https://lore.kernel.org/r/20250204004038.1680123-3-jthoughton@google.com
[sean: massage shortlog+changelog, fix Kconfig goof and shorten name]
Signed-off-by: Sean Christopherson <seanjc@google.com>
Diffstat (limited to 'virt')
| -rw-r--r-- | virt/kvm/Kconfig | 4 | ||||
| -rw-r--r-- | virt/kvm/kvm_main.c | 23 |
2 files changed, 20 insertions, 7 deletions
diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig index 54e959e7d68f..746e1f466aa6 100644 --- a/virt/kvm/Kconfig +++ b/virt/kvm/Kconfig @@ -104,6 +104,10 @@ config KVM_ELIDE_TLB_FLUSH_IF_YOUNG depends on KVM_GENERIC_MMU_NOTIFIER bool +config KVM_MMU_LOCKLESS_AGING + depends on KVM_GENERIC_MMU_NOTIFIER + bool + config KVM_GENERIC_MEMORY_ATTRIBUTES depends on KVM_GENERIC_MMU_NOTIFIER bool diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 0f94349f99e2..201c14ff476f 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -517,6 +517,7 @@ struct kvm_mmu_notifier_range { on_lock_fn_t on_lock; bool flush_on_ret; bool may_block; + bool lockless; }; /* @@ -571,6 +572,10 @@ static __always_inline kvm_mn_ret_t kvm_handle_hva_range(struct kvm *kvm, IS_KVM_NULL_FN(range->handler))) return r; + /* on_lock will never be called for lockless walks */ + if (WARN_ON_ONCE(range->lockless && !IS_KVM_NULL_FN(range->on_lock))) + return r; + idx = srcu_read_lock(&kvm->srcu); for (i = 0; i < kvm_arch_nr_memslot_as_ids(kvm); i++) { @@ -607,15 +612,18 @@ static __always_inline kvm_mn_ret_t kvm_handle_hva_range(struct kvm *kvm, gfn_range.start = hva_to_gfn_memslot(hva_start, slot); gfn_range.end = hva_to_gfn_memslot(hva_end + PAGE_SIZE - 1, slot); gfn_range.slot = slot; + gfn_range.lockless = range->lockless; if (!r.found_memslot) { r.found_memslot = true; - KVM_MMU_LOCK(kvm); - if (!IS_KVM_NULL_FN(range->on_lock)) - range->on_lock(kvm); - - if (IS_KVM_NULL_FN(range->handler)) - goto mmu_unlock; + if (!range->lockless) { + KVM_MMU_LOCK(kvm); + if (!IS_KVM_NULL_FN(range->on_lock)) + range->on_lock(kvm); + + if (IS_KVM_NULL_FN(range->handler)) + goto mmu_unlock; + } } r.ret |= range->handler(kvm, &gfn_range); } @@ -625,7 +633,7 @@ static __always_inline kvm_mn_ret_t kvm_handle_hva_range(struct kvm *kvm, kvm_flush_remote_tlbs(kvm); mmu_unlock: - if (r.found_memslot) + if (r.found_memslot && !range->lockless) KVM_MMU_UNLOCK(kvm); srcu_read_unlock(&kvm->srcu, idx); @@ -647,6 +655,7 @@ static __always_inline int kvm_age_hva_range(struct mmu_notifier *mn, .on_lock = (void *)kvm_null_fn, .flush_on_ret = flush_on_ret, .may_block = false, + .lockless = IS_ENABLED(CONFIG_KVM_MMU_LOCKLESS_AGING), }; return kvm_handle_hva_range(kvm, &range).ret; |