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([2a01:e0a:59e:9d80:527b:9dff:feef:3874]) by smtp.gmail.com with ESMTPSA id v191sm271021wme.36.2021.11.10.09.00.22 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 10 Nov 2021 09:00:23 -0800 (PST) Subject: Re: [PATCH v4 03/15] KVM: async_pf: Make GFN slot management generic To: Gavin Shan , kvmarm@lists.cs.columbia.edu Cc: kvm@vger.kernel.org, maz@kernel.org, linux-kernel@vger.kernel.org, shan.gavin@gmail.com, Jonathan.Cameron@huawei.com, pbonzini@redhat.com, vkuznets@redhat.com, will@kernel.org References: <20210815005947.83699-1-gshan@redhat.com> <20210815005947.83699-4-gshan@redhat.com> From: Eric Auger Message-ID: <3e36bb05-90ce-9448-14c8-172313b986b7@redhat.com> Date: Wed, 10 Nov 2021 18:00:22 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: <20210815005947.83699-4-gshan@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Gavin, On 8/15/21 2:59 AM, Gavin Shan wrote: > It's not allowed to fire duplicate notification for same GFN on > x86 platform, with help of a hash table. This mechanism is going s/, with help of a hash table/this is achieved through a hash table > to be used by arm64 and this makes the code generic and shareable s/and this makes/.\n Turn the code generic > by multiple platforms. > > * As this mechanism isn't needed by all platforms, a new kernel > config option (CONFIG_ASYNC_PF_SLOT) is introduced so that it > can be disabled at compiling time. compile time > > * The code is basically copied from x86 platform and the functions > are renamed to reflect the fact: (a) the input parameters are > vCPU and GFN. not for reset (b) The operations are resetting, searching, adding > and removing. find, add, remove ops are renamed with _slot suffix > > * Helper stub is also added on !CONFIG_KVM_ASYNC_PF because we're > going to use IS_ENABLED() instead of #ifdef on arm64 when the > asynchronous page fault is supported. > > This is preparatory work to use the newly introduced functions on x86 > platform and arm64 in subsequent patches. > > Signed-off-by: Gavin Shan > --- > include/linux/kvm_host.h | 18 +++++++++ > virt/kvm/Kconfig | 3 ++ > virt/kvm/async_pf.c | 85 ++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 106 insertions(+) > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index a5f990f6dc35..a9685c2b2250 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -298,6 +298,9 @@ struct kvm_vcpu { > > #ifdef CONFIG_KVM_ASYNC_PF > struct { > +#ifdef CONFIG_KVM_ASYNC_PF_SLOT > + gfn_t gfns[ASYNC_PF_PER_VCPU]; > +#endif > u32 queued; > struct list_head queue; > struct list_head done; > @@ -339,6 +342,13 @@ struct kvm_async_pf { > bool notpresent_injected; > }; > > +#ifdef CONFIG_KVM_ASYNC_PF_SLOT > +void kvm_async_pf_reset_slot(struct kvm_vcpu *vcpu); this does not reset a "slot" but the whole hash table. So to me this shouldn't be renamed with _slot suffix. reset_hash or reset_all_slots? > +void kvm_async_pf_add_slot(struct kvm_vcpu *vcpu, gfn_t gfn); > +void kvm_async_pf_remove_slot(struct kvm_vcpu *vcpu, gfn_t gfn); > +bool kvm_async_pf_find_slot(struct kvm_vcpu *vcpu, gfn_t gfn); > +#endif > + > static inline bool kvm_check_async_pf_completion_queue(struct kvm_vcpu *vcpu) > { > return !list_empty_careful(&vcpu->async_pf.done); > @@ -350,6 +360,14 @@ bool kvm_setup_async_pf(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, > unsigned long hva, struct kvm_arch_async_pf *arch); > int kvm_async_pf_wakeup_all(struct kvm_vcpu *vcpu); > #else > +static inline void kvm_async_pf_reset_slot(struct kvm_vcpu *vcpu) { } > +static inline void kvm_async_pf_add_slot(struct kvm_vcpu *vcpu, gfn_t gfn) { } > +static inline void kvm_async_pf_remove_slot(struct kvm_vcpu *vcpu, gfn_t gfn) { } > +static inline bool kvm_async_pf_find_slot(struct kvm_vcpu *vcpu, gfn_t gfn) > +{ > + return false; > +} > + > static inline bool kvm_check_async_pf_completion_queue(struct kvm_vcpu *vcpu) > { > return false; > diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig > index 62b39149b8c8..59b518c8c205 100644 > --- a/virt/kvm/Kconfig > +++ b/virt/kvm/Kconfig > @@ -23,6 +23,9 @@ config KVM_MMIO > config KVM_ASYNC_PF > bool > > +config KVM_ASYNC_PF_SLOT > + bool > + > # Toggle to switch between direct notification and batch job > config KVM_ASYNC_PF_SYNC > bool > diff --git a/virt/kvm/async_pf.c b/virt/kvm/async_pf.c > index d145a61a046a..0d1fdb2932af 100644 > --- a/virt/kvm/async_pf.c > +++ b/virt/kvm/async_pf.c > @@ -13,12 +13,97 @@ > #include > #include > #include > +#ifdef CONFIG_KVM_ASYNC_PF_SLOT > +#include > +#endif > > #include "async_pf.h" > #include > > static struct kmem_cache *async_pf_cache; > > +#ifdef CONFIG_KVM_ASYNC_PF_SLOT > +static inline u32 kvm_async_pf_hash(gfn_t gfn) > +{ > + BUILD_BUG_ON(!is_power_of_2(ASYNC_PF_PER_VCPU)); > + > + return hash_32(gfn & 0xffffffff, order_base_2(ASYNC_PF_PER_VCPU)); > +} > + > +static inline u32 kvm_async_pf_next_slot(u32 key) > +{ > + return (key + 1) & (ASYNC_PF_PER_VCPU - 1); > +} > + > +static u32 kvm_async_pf_slot(struct kvm_vcpu *vcpu, gfn_t gfn) > +{ > + u32 key = kvm_async_pf_hash(gfn); > + int i; > + > + for (i = 0; i < ASYNC_PF_PER_VCPU && > + (vcpu->async_pf.gfns[key] != gfn && > + vcpu->async_pf.gfns[key] != ~0); i++) > + key = kvm_async_pf_next_slot(key); > + > + return key; > +} > + > +void kvm_async_pf_reset_slot(struct kvm_vcpu *vcpu) > +{ > + int i; > + > + for (i = 0; i < ASYNC_PF_PER_VCPU; i++) > + vcpu->async_pf.gfns[i] = ~0; > +} > + > +void kvm_async_pf_add_slot(struct kvm_vcpu *vcpu, gfn_t gfn) > +{ > + u32 key = kvm_async_pf_hash(gfn); > + > + while (vcpu->async_pf.gfns[key] != ~0) > + key = kvm_async_pf_next_slot(key); > + > + vcpu->async_pf.gfns[key] = gfn; > +} > + > +void kvm_async_pf_remove_slot(struct kvm_vcpu *vcpu, gfn_t gfn) > +{ > + u32 i, j, k; > + > + i = j = kvm_async_pf_slot(vcpu, gfn); > + > + if (WARN_ON_ONCE(vcpu->async_pf.gfns[i] != gfn)) > + return; > + > + while (true) { > + vcpu->async_pf.gfns[i] = ~0; > + > + do { > + j = kvm_async_pf_next_slot(j); > + if (vcpu->async_pf.gfns[j] == ~0) > + return; > + > + k = kvm_async_pf_hash(vcpu->async_pf.gfns[j]); > + /* > + * k lies cyclically in ]i,j] > + * | i.k.j | > + * |....j i.k.| or |.k..j i...| > + */ > + } while ((i <= j) ? (i < k && k <= j) : (i < k || k <= j)); > + > + vcpu->async_pf.gfns[i] = vcpu->async_pf.gfns[j]; > + i = j; > + } > +} > + > +bool kvm_async_pf_find_slot(struct kvm_vcpu *vcpu, gfn_t gfn) > +{ > + u32 key = kvm_async_pf_slot(vcpu, gfn); > + > + return vcpu->async_pf.gfns[key] == gfn; > +} > +#endif /* CONFIG_KVM_ASYNC_PF_SLOT */ > + > int kvm_async_pf_init(void) > { > async_pf_cache = KMEM_CACHE(kvm_async_pf, 0); > Thanks Eric