This is a note to let you know that I've just added the patch titled
KVM: x86: make KVM_REQ_NMI request iff NMI pending for vcpu
to the 6.7-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kvm-x86-make-kvm_req_nmi-request-iff-nmi-pending-for-vcpu.patch
and it can be found in the queue-6.7 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 6231c9e1a9f35b535c66709aa8a6eda40dbc4132 Mon Sep 17 00:00:00 2001
From: Prasad Pandit <pjp@xxxxxxxxxxxxxxxxx>
Date: Wed, 3 Jan 2024 13:23:43 +0530
Subject: KVM: x86: make KVM_REQ_NMI request iff NMI pending for vcpu
From: Prasad Pandit <pjp@xxxxxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxx
Signed-off-by: Prasad Pandit <pjp@xxxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20240103075343.549293-1-ppandit@xxxxxxxxxx
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kvm/x86.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5405,7 +5405,8 @@ static int kvm_vcpu_ioctl_x86_set_vcpu_e
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);
Patches currently in stable-queue which might be from pjp@xxxxxxxxxxxxxxxxx are
queue-6.7/kvm-x86-make-kvm_req_nmi-request-iff-nmi-pending-for-vcpu.patch
