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[35.185.214.157]) by smtp.gmail.com with ESMTPSA id n13sm3053146pff.164.2021.09.02.14.19.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 02 Sep 2021 14:19:30 -0700 (PDT) Date: Thu, 2 Sep 2021 21:19:26 +0000 From: Sean Christopherson To: Vitaly Kuznetsov Cc: kvm@vger.kernel.org, Paolo Bonzini , Wanpeng Li , Jim Mattson , "Dr. David Alan Gilbert" , Nitesh Narayan Lal , Lai Jiangshan , Maxim Levitsky , Eduardo Habkost , linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 8/8] KVM: Make kvm_make_vcpus_request_mask() use pre-allocated cpu_kick_mask Message-ID: References: <20210827092516.1027264-1-vkuznets@redhat.com> <20210827092516.1027264-9-vkuznets@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210827092516.1027264-9-vkuznets@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 27, 2021, Vitaly Kuznetsov wrote: > kvm_make_vcpus_request_mask() already disables preemption so just like > kvm_make_all_cpus_request_except() it can be switched to using > pre-allocated per-cpu cpumasks. This allows for improvements for both > users of the function: in Hyper-V emulation code 'tlb_flush' can now be > dropped from 'struct kvm_vcpu_hv' and kvm_make_scan_ioapic_request_mask() > gets rid of dynamic allocation. > > cpumask_available() check in kvm_make_vcpu_request() can now be dropped as > it checks for an impossible condition: kvm_init() makes sure per-cpu masks > are allocated. > > Signed-off-by: Vitaly Kuznetsov > --- > arch/x86/include/asm/kvm_host.h | 1 - > arch/x86/kvm/hyperv.c | 5 +---- > arch/x86/kvm/x86.c | 8 +------- > include/linux/kvm_host.h | 2 +- > virt/kvm/kvm_main.c | 18 +++++++----------- > 5 files changed, 10 insertions(+), 24 deletions(-) > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > index 09b256db394a..846552fa2012 100644 > --- a/arch/x86/include/asm/kvm_host.h > +++ b/arch/x86/include/asm/kvm_host.h > @@ -569,7 +569,6 @@ struct kvm_vcpu_hv { > struct kvm_hyperv_exit exit; > struct kvm_vcpu_hv_stimer stimer[HV_SYNIC_STIMER_COUNT]; > DECLARE_BITMAP(stimer_pending_bitmap, HV_SYNIC_STIMER_COUNT); > - cpumask_t tlb_flush; > bool enforce_cpuid; > struct { > u32 features_eax; /* HYPERV_CPUID_FEATURES.EAX */ > diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c > index 5704bfe53ee0..f76e7228f687 100644 > --- a/arch/x86/kvm/hyperv.c > +++ b/arch/x86/kvm/hyperv.c > @@ -1755,7 +1755,6 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc, bool > int i; > gpa_t gpa; > struct kvm *kvm = vcpu->kvm; > - struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu); > struct hv_tlb_flush_ex flush_ex; > struct hv_tlb_flush flush; > u64 vp_bitmap[KVM_HV_MAX_SPARSE_VCPU_SET_BITS]; > @@ -1837,8 +1836,6 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc, bool > } > } > > - cpumask_clear(&hv_vcpu->tlb_flush); > - > /* > * vcpu->arch.cr3 may not be up-to-date for running vCPUs so we can't > * analyze it here, flush TLB regardless of the specified address space. > @@ -1850,7 +1847,7 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc, bool > vp_bitmap, vcpu_bitmap); > > kvm_make_vcpus_request_mask(kvm, KVM_REQ_TLB_FLUSH_GUEST, > - vcpu_mask, &hv_vcpu->tlb_flush); > + vcpu_mask); > } > > ret_success: > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index a4752dcc2a75..91c1e6c98b0f 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -9224,14 +9224,8 @@ static void process_smi(struct kvm_vcpu *vcpu) > void kvm_make_scan_ioapic_request_mask(struct kvm *kvm, > unsigned long *vcpu_bitmap) > { > - cpumask_var_t cpus; > - > - zalloc_cpumask_var(&cpus, GFP_ATOMIC); > - > kvm_make_vcpus_request_mask(kvm, KVM_REQ_SCAN_IOAPIC, > - vcpu_bitmap, cpus); > - > - free_cpumask_var(cpus); > + vcpu_bitmap); This can opportunistically all go on a single line. > } > > void kvm_make_scan_ioapic_request(struct kvm *kvm) > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index 2f149ed140f7..1ee85de0bf74 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -160,7 +160,7 @@ static inline bool is_error_page(struct page *page) > #define KVM_ARCH_REQ(nr) KVM_ARCH_REQ_FLAGS(nr, 0) > > bool kvm_make_vcpus_request_mask(struct kvm *kvm, unsigned int req, > - unsigned long *vcpu_bitmap, cpumask_var_t tmp); > + unsigned long *vcpu_bitmap); > bool kvm_make_all_cpus_request(struct kvm *kvm, unsigned int req); > bool kvm_make_all_cpus_request_except(struct kvm *kvm, unsigned int req, > struct kvm_vcpu *except); > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 2f5fe4f54a51..dc52a04f0586 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -274,14 +274,6 @@ static void kvm_make_vcpu_request(struct kvm *kvm, struct kvm_vcpu *vcpu, > if (!(req & KVM_REQUEST_NO_WAKEUP) && kvm_vcpu_wake_up(vcpu)) > return; > > - /* > - * tmp can be "unavailable" if cpumasks are allocated off stack as > - * allocation of the mask is deliberately not fatal and is handled by > - * falling back to kicking all online CPUs. > - */ > - if (!cpumask_available(tmp)) > - return; Hmm, maybe convert the param to an explicit "struct cpumask *" to try and convey that cpumask_available() doesn't need to be checked? And I believe you can also do: diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index dc52a04f0586..bfd2ecbd97a8 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -247,15 +247,8 @@ static void ack_flush(void *_completed) { } -static inline bool kvm_kick_many_cpus(cpumask_var_t tmp, bool wait) +static inline bool kvm_kick_many_cpus(struct cpumask *cpus, bool wait) { - const struct cpumask *cpus; - - if (likely(cpumask_available(tmp))) - cpus = tmp; - else - cpus = cpu_online_mask; - if (cpumask_empty(cpus)) return false; > - > /* > * Note, the vCPU could get migrated to a different pCPU at any point > * after kvm_request_needs_ipi(), which could result in sending an IPI > @@ -300,22 +292,26 @@ static void kvm_make_vcpu_request(struct kvm *kvm, struct kvm_vcpu *vcpu, > } > > bool kvm_make_vcpus_request_mask(struct kvm *kvm, unsigned int req, > - unsigned long *vcpu_bitmap, cpumask_var_t tmp) > + unsigned long *vcpu_bitmap) > { > struct kvm_vcpu *vcpu; > + struct cpumask *cpus; > int i, me; > bool called; > > me = get_cpu(); > > + cpus = this_cpu_cpumask_var_ptr(cpu_kick_mask); > + cpumask_clear(cpus); > + > for_each_set_bit(i, vcpu_bitmap, KVM_MAX_VCPUS) { > vcpu = kvm_get_vcpu(kvm, i); > if (!vcpu) > continue; > - kvm_make_vcpu_request(kvm, vcpu, req, tmp, me); > + kvm_make_vcpu_request(kvm, vcpu, req, cpus, me); > } > > - called = kvm_kick_many_cpus(tmp, !!(req & KVM_REQUEST_WAIT)); > + called = kvm_kick_many_cpus(cpus, !!(req & KVM_REQUEST_WAIT)); > put_cpu(); > > return called; > -- > 2.31.1 >