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AJvYcCXOQOis/lxGYXEPnT51v7sHy8XNZAlE1/yNmObiANwHYfEJeTQb8xGRiKtj1ZXM4zsHHNRwopN26KiYvz1hdwLIf4iAwGs5WcUBaVIU X-Gm-Message-State: AOJu0YzeCNBMogrX562Q7R0uKnt6eke3+NbEkRR8rg075a9bQK0Dy04m QLs/G7yHMaOZscXC7rENk5Vlaw0E4rzcWmvEUbQzdnPq7h70cm+viL66/Mj5XUQSAZNtMiP9JuS PwI05BozSr/i2z1vEpg== X-Google-Smtp-Source: AGHT+IFU0dcKvF1oJPyuhM+g7ff3d/ALiIFFaW2tweOW7lf82u7TeCdfrHDEq+idZRCqJG0SfkAoO+hAK8jfDIhe X-Received: from jthoughton.c.googlers.com ([fda3:e722:ac3:cc00:14:4d90:c0a8:2a4f]) (user=jthoughton job=sendgmr) by 2002:a05:6102:54a5:b0:492:a760:c94c with SMTP id ada2fe7eead31-493c199efb7mr42818137.4.1721783474197; Tue, 23 Jul 2024 18:11:14 -0700 (PDT) Date: Wed, 24 Jul 2024 01:10:26 +0000 In-Reply-To: <20240724011037.3671523-1-jthoughton@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240724011037.3671523-1-jthoughton@google.com> X-Mailer: git-send-email 2.46.0.rc1.232.g9752f9e123-goog Message-ID: <20240724011037.3671523-2-jthoughton@google.com> Subject: [PATCH v6 01/11] KVM: Add lockless memslot walk to KVM From: James Houghton To: Andrew Morton , Paolo Bonzini Cc: Ankit Agrawal , Axel Rasmussen , Catalin Marinas , David Matlack , David Rientjes , James Houghton , James Morse , Jason Gunthorpe , Jonathan Corbet , Marc Zyngier , Oliver Upton , Raghavendra Rao Ananta , Ryan Roberts , Sean Christopherson , Shaoqin Huang , Suzuki K Poulose , Wei Xu , Will Deacon , Yu Zhao , Zenghui Yu , kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Provide flexibility to the architecture to synchronize as optimally as they can instead of always taking the MMU lock for writing. Architectures that do their own locking must select CONFIG_KVM_MMU_NOTIFIER_YOUNG_LOCKLESS. The immediate application is to allow architectures to implement the test/clear_young MMU notifiers more cheaply. Suggested-by: Yu Zhao Signed-off-by: James Houghton Reviewed-by: David Matlack --- include/linux/kvm_host.h | 1 + virt/kvm/Kconfig | 3 +++ virt/kvm/kvm_main.c | 26 +++++++++++++++++++------- 3 files changed, 23 insertions(+), 7 deletions(-) diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 689e8be873a7..8cd80f969cff 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -266,6 +266,7 @@ struct kvm_gfn_range { gfn_t end; union kvm_mmu_notifier_arg arg; bool may_block; + bool lockless; }; bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range); bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range); diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig index b14e14cdbfb9..632334861001 100644 --- a/virt/kvm/Kconfig +++ b/virt/kvm/Kconfig @@ -100,6 +100,9 @@ config KVM_GENERIC_MMU_NOTIFIER select MMU_NOTIFIER bool =20 +config KVM_MMU_NOTIFIER_YOUNG_LOCKLESS + 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 d0788d0a72cc..33f8997a5c29 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -555,6 +555,7 @@ struct kvm_mmu_notifier_range { on_lock_fn_t on_lock; bool flush_on_ret; bool may_block; + bool lockless; }; =20 /* @@ -609,6 +610,10 @@ static __always_inline kvm_mn_ret_t __kvm_handle_hva_r= ange(struct kvm *kvm, IS_KVM_NULL_FN(range->handler))) return r; =20 + /* 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 =3D srcu_read_lock(&kvm->srcu); =20 for (i =3D 0; i < kvm_arch_nr_memslot_as_ids(kvm); i++) { @@ -640,15 +645,18 @@ static __always_inline kvm_mn_ret_t __kvm_handle_hva_= range(struct kvm *kvm, gfn_range.start =3D hva_to_gfn_memslot(hva_start, slot); gfn_range.end =3D hva_to_gfn_memslot(hva_end + PAGE_SIZE - 1, slot); gfn_range.slot =3D slot; + gfn_range.lockless =3D range->lockless; =20 if (!r.found_memslot) { r.found_memslot =3D 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 |=3D range->handler(kvm, &gfn_range); } @@ -658,7 +666,7 @@ static __always_inline kvm_mn_ret_t __kvm_handle_hva_ra= nge(struct kvm *kvm, kvm_flush_remote_tlbs(kvm); =20 mmu_unlock: - if (r.found_memslot) + if (r.found_memslot && !range->lockless) KVM_MMU_UNLOCK(kvm); =20 srcu_read_unlock(&kvm->srcu, idx); @@ -679,6 +687,8 @@ static __always_inline int kvm_handle_hva_range(struct = mmu_notifier *mn, .on_lock =3D (void *)kvm_null_fn, .flush_on_ret =3D true, .may_block =3D false, + .lockless =3D + IS_ENABLED(CONFIG_KVM_MMU_NOTIFIER_YOUNG_LOCKLESS), }; =20 return __kvm_handle_hva_range(kvm, &range).ret; @@ -697,6 +707,8 @@ static __always_inline int kvm_handle_hva_range_no_flus= h(struct mmu_notifier *mn .on_lock =3D (void *)kvm_null_fn, .flush_on_ret =3D false, .may_block =3D false, + .lockless =3D + IS_ENABLED(CONFIG_KVM_MMU_NOTIFIER_YOUNG_LOCKLESS), }; =20 return __kvm_handle_hva_range(kvm, &range).ret; --=20 2.46.0.rc1.232.g9752f9e123-goog