KVM: Make kvm_make_vcpus_request_mask() use pre-allocated cpu_kick_mask

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() checks in kvm_make_vcpu_request() and
kvm_kick_many_cpus() can now be dropped as they checks for an impossible
condition: kvm_init() makes sure per-cpu masks are allocated.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210903075141.403071-9-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index f8f48a7ec577f64d2af855f58e0467768f091ccc..120ac07e4094437b39ce523ab852efa96c3334ad 100644 (file)
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -581,7 +581,6 @@ 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 b4b432a164aefac75c020c87cc826afb11232fb8..6f11cda2bfa467f7608f5cd51147e05b4e379372 100644 (file)
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1754,7 +1754,6 @@ 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];
@@ -1836,8 +1835,6 @@ 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.
@@ -1849,7 +1846,7 @@ 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 7212ba654ba2337612186da5fe44113cbd2ef6f7..03568cbbe8bd48e2636da55c2f2dfcfee2c16047 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9242,14 +9242,7 @@ 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);
+       kvm_make_vcpus_request_mask(kvm, KVM_REQ_SCAN_IOAPIC, vcpu_bitmap);
 }
 
 void kvm_make_scan_ioapic_request(struct kvm *kvm)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 89e1a0069833a704b9dcf05737c9f69b91e41ab4..f1b96a2ebaa7e0011db1bb85f286a932a6d43978 100644 (file)
--- 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 9cb0fd1723e6d484e8715aba1f9cf40c20163b31..18d245fe211845a649a8b5cb2e4eac4d550126ff 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -237,15 +237,8 @@ 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;
 
@@ -254,7 +247,7 @@ static inline bool kvm_kick_many_cpus(cpumask_var_t tmp, bool wait)
 }
 
 static void kvm_make_vcpu_request(struct kvm *kvm, struct kvm_vcpu *vcpu,
-                                 unsigned int req, cpumask_var_t tmp,
+                                 unsigned int req, struct cpumask *tmp,
                                  int current_cpu)
 {
        int cpu;
@@ -264,14 +257,6 @@ 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;
-
        /*
         * 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
@@ -290,22 +275,26 @@ 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;