From: Prasad Pandit <ppandit@redhat.com>
To: Sean Christopherson <seanjc@google.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Prasad Pandit <pjp@fedoraproject.org>
Subject: [PATCH] KVM: x86: make KVM_REQ_NMI request iff NMI pending for vcpu
Date: Wed, 3 Jan 2024 13:23:43 +0530 [thread overview]
Message-ID: <20240103075343.549293-1-ppandit@redhat.com> (raw)
From: Prasad Pandit <pjp@fedoraproject.org>
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()")
Signed-off-by: Prasad Pandit <pjp@fedoraproject.org>
---
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 1a3aaa7dafae..468870450b8b 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5405,7 +5405,8 @@ 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);
--
2.43.0
next reply other threads:[~2024-01-03 7:53 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-03 7:53 Prasad Pandit [this message]
2024-01-08 10:45 ` [PATCH] KVM: x86: make KVM_REQ_NMI request iff NMI pending for vcpu Prasad Pandit
2024-01-08 17:38 ` Sean Christopherson
2024-01-09 6:26 ` Prasad Pandit
2024-02-03 0:11 ` Sean Christopherson
2024-02-06 8:10 ` Dongli Zhang
2024-02-06 20:58 ` Sean Christopherson
2024-02-09 0:34 ` Dongli Zhang
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