From eea9b2e0d22211b3413606519b34ca4ea4dad9f0 Mon Sep 17 00:00:00 2001 From: Prasad Pandit Date: Wed, 3 Jan 2024 13:23:43 +0530 Subject: [PATCH] KVM: x86: make KVM_REQ_NMI request iff NMI pending for vcpu commit 6231c9e1a9f35b535c66709aa8a6eda40dbc4132 upstream. kvm_vcpu_ioctl_x86_set_vcpu_events() routine makes 'KVM_REQ_NMI' request for a vcpu even when its 'events->nmi.pending' is zero. Ex: qemu_thread_start kvm_vcpu_thread_fn qemu_wait_io_event qemu_wait_io_event_common process_queued_cpu_work do_kvm_cpu_synchronize_post_init/_reset kvm_arch_put_registers kvm_put_vcpu_events (cpu, level=[2|3]) This leads vCPU threads in QEMU to constantly acquire & release the global mutex lock, delaying the guest boot due to lock contention. Add check to make KVM_REQ_NMI request only if vcpu has NMI pending. Fixes: bdedff263132 ("KVM: x86: Route pending NMIs from userspace through process_nmi()") Cc: stable@vger.kernel.org Signed-off-by: Prasad Pandit Link: https://lore.kernel.org/r/20240103075343.549293-1-ppandit@redhat.com Signed-off-by: Sean Christopherson Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/x86.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index e179db7c17da..3d8472d00024 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -5300,7 +5300,8 @@ static int kvm_vcpu_ioctl_x86_set_vcpu_events(struct kvm_vcpu *vcpu, if (events->flags & KVM_VCPUEVENT_VALID_NMI_PENDING) { vcpu->arch.nmi_pending = 0; atomic_set(&vcpu->arch.nmi_queued, events->nmi.pending); - kvm_make_request(KVM_REQ_NMI, vcpu); + if (events->nmi.pending) + kvm_make_request(KVM_REQ_NMI, vcpu); } static_call(kvm_x86_set_nmi_mask)(vcpu, events->nmi.masked);