From: Sean Christopherson Date: Wed, 8 Dec 2021 01:52:34 +0000 (+0000) Subject: KVM: x86: Skip APICv update if APICv is disable at the module level X-Git-Tag: v5.18-rc1~10^2~218 X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=f15756428ded1ee01d95934057a6e89c2d450bbb;p=linux-block.git KVM: x86: Skip APICv update if APICv is disable at the module level Bail from the APICv update paths _before_ taking apicv_update_lock if APICv is disabled at the module level. kvm_request_apicv_update() in particular is invoked from multiple paths that can be reached without APICv being enabled, e.g. svm_enable_irq_window(), and taking the rw_sem for write when APICv is disabled may introduce unnecessary contention and stalls. Signed-off-by: Sean Christopherson Message-Id: <20211208015236.1616697-25-seanjc@google.com> Signed-off-by: Paolo Bonzini --- diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c index 6e38a7d22e97..0bc7488f2b39 100644 --- a/arch/x86/kvm/hyperv.c +++ b/arch/x86/kvm/hyperv.c @@ -112,6 +112,9 @@ static void synic_update_vector(struct kvm_vcpu_hv_synic *synic, if (!!auto_eoi_old == !!auto_eoi_new) return; + if (!enable_apicv) + return; + down_write(&vcpu->kvm->arch.apicv_update_lock); if (auto_eoi_new) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 3b7479bd3404..04d3f8abc3ad 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -9715,6 +9715,9 @@ void __kvm_request_apicv_update(struct kvm *kvm, bool activate, ulong bit) void kvm_request_apicv_update(struct kvm *kvm, bool activate, ulong bit) { + if (!enable_apicv) + return; + down_write(&kvm->arch.apicv_update_lock); __kvm_request_apicv_update(kvm, activate, bit); up_write(&kvm->arch.apicv_update_lock);