The shortlog should be: KVM: x86: Drop the kvm_has_noapic_vcpu optimization see https://docs.kernel.org/process/maintainer-kvm-x86.html#shortlog On Fri, Oct 18, 2024 at 12:08:45PM +0200, Bernhard Kauer wrote: >It used a static key to avoid loading the lapic pointer from >the vcpu->arch structure. However, in the common case the load >is from a hot cacheline and the CPU should be able to perfectly >predict it. Thus there is no upside of this premature optimization. > >The downside is that code patching including an IPI to all CPUs >is required whenever the first VM without an lapic is created or >the last is destroyed. > >Signed-off-by: Bernhard Kauer <bk@xxxxxxxxx> >--- > arch/x86/kvm/lapic.c | 4 ---- > arch/x86/kvm/lapic.h | 6 +----- > arch/x86/kvm/x86.c | 8 -------- > 3 files changed, 1 insertion(+), 17 deletions(-) > >diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c >index 2098dc689088..0c75b3cc01f2 100644 >--- a/arch/x86/kvm/lapic.c >+++ b/arch/x86/kvm/lapic.c >@@ -135,8 +135,6 @@ static inline int __apic_test_and_clear_vector(int vec, void *bitmap) > return __test_and_clear_bit(VEC_POS(vec), (bitmap) + REG_POS(vec)); > } > >-__read_mostly DEFINE_STATIC_KEY_FALSE(kvm_has_noapic_vcpu); >-EXPORT_SYMBOL_GPL(kvm_has_noapic_vcpu); > > __read_mostly DEFINE_STATIC_KEY_DEFERRED_FALSE(apic_hw_disabled, HZ); > __read_mostly DEFINE_STATIC_KEY_DEFERRED_FALSE(apic_sw_disabled, HZ); >@@ -2518,7 +2516,6 @@ void kvm_free_lapic(struct kvm_vcpu *vcpu) > struct kvm_lapic *apic = vcpu->arch.apic; > > if (!vcpu->arch.apic) { >- static_branch_dec(&kvm_has_noapic_vcpu); > return; > } remove the curly brackets, i.e., just if (!vcpu->arch.apic) return; > >@@ -2864,7 +2861,6 @@ int kvm_create_lapic(struct kvm_vcpu *vcpu) > ASSERT(vcpu != NULL); > > if (!irqchip_in_kernel(vcpu->kvm)) { >- static_branch_inc(&kvm_has_noapic_vcpu); > return 0; > } ditto > >diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h >index 1b8ef9856422..157af18c9fc8 100644 >--- a/arch/x86/kvm/lapic.h >+++ b/arch/x86/kvm/lapic.h >@@ -179,13 +179,9 @@ static inline u32 kvm_lapic_get_reg(struct kvm_lapic *apic, int reg_off) > return __kvm_lapic_get_reg(apic->regs, reg_off); > } > >-DECLARE_STATIC_KEY_FALSE(kvm_has_noapic_vcpu); >- > static inline bool lapic_in_kernel(struct kvm_vcpu *vcpu) > { >- if (static_branch_unlikely(&kvm_has_noapic_vcpu)) >- return vcpu->arch.apic; >- return true; >+ return vcpu->arch.apic; > } > > extern struct static_key_false_deferred apic_hw_disabled; >diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c >index 83fe0a78146f..ca73cae31f53 100644 >--- a/arch/x86/kvm/x86.c >+++ b/arch/x86/kvm/x86.c >@@ -9828,8 +9828,6 @@ void kvm_x86_vendor_exit(void) > if (hypervisor_is_type(X86_HYPER_MS_HYPERV)) > clear_hv_tscchange_cb(); > #endif >- kvm_lapic_exit(); >- why is this call removed? > if (!boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) { > cpufreq_unregister_notifier(&kvmclock_cpufreq_notifier_block, > CPUFREQ_TRANSITION_NOTIFIER); >@@ -14015,9 +14013,3 @@ static int __init kvm_x86_init(void) > return 0; > } > module_init(kvm_x86_init); >- >-static void __exit kvm_x86_exit(void) >-{ >- WARN_ON_ONCE(static_branch_unlikely(&kvm_has_noapic_vcpu)); >-} >-module_exit(kvm_x86_exit); >-- >2.45.2 > >
