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Prasad Pandit eea9b2e0d2 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 <pjp@fedoraproject.org>
Link: https://lore.kernel.org/r/20240103075343.549293-1-ppandit@redhat.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2024-02-23 09:25:10 +01:00

alpha

rtc: Add support for configuring the UIP timeout for RTC reads

2024-01-31 16:18:56 -08:00

arc

work around gcc bugs with 'asm goto' with outputs

2024-02-23 09:24:47 +01:00

arm

work around gcc bugs with 'asm goto' with outputs

2024-02-23 09:24:47 +01:00

arm64

work around gcc bugs with 'asm goto' with outputs