Merge tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm

Pull KVM fixes from Paolo Bonzini:
 "Bugfixes and improvements to selftests.

  On top of this, Mauro converted the KVM documentation to rst format,
  which was very welcome"

* tag 'for-linus' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (44 commits)
  docs: virt: guest-halt-polling.txt convert to ReST
  docs: kvm: review-checklist.txt: rename to ReST
  docs: kvm: Convert timekeeping.txt to ReST format
  docs: kvm: Convert s390-diag.txt to ReST format
  docs: kvm: Convert ppc-pv.txt to ReST format
  docs: kvm: Convert nested-vmx.txt to ReST format
  docs: kvm: Convert mmu.txt to ReST format
  docs: kvm: Convert locking.txt to ReST format
  docs: kvm: Convert hypercalls.txt to ReST format
  docs: kvm: arm/psci.txt: convert to ReST
  docs: kvm: convert arm/hyp-abi.txt to ReST
  docs: kvm: Convert api.txt to ReST format
  docs: kvm: convert devices/xive.txt to ReST
  docs: kvm: convert devices/xics.txt to ReST
  docs: kvm: convert devices/vm.txt to ReST
  docs: kvm: convert devices/vfio.txt to ReST
  docs: kvm: convert devices/vcpu.txt to ReST
  docs: kvm: convert devices/s390_flic.txt to ReST
  docs: kvm: convert devices/mpic.txt to ReST
  docs: kvm: convert devices/arm-vgit.txt to ReST
  ...

1 files changed, 13 insertions, 3 deletions

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 67ae2d5c37b2..70f03ce0e5c1 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -4409,12 +4409,22 @@ static void kvm_sched_out(struct preempt_notifier *pn,
 
 /**
  * kvm_get_running_vcpu - get the vcpu running on the current CPU.
- * Thanks to preempt notifiers, this can also be called from
- * preemptible context.
+ *
+ * We can disable preemption locally around accessing the per-CPU variable,
+ * and use the resolved vcpu pointer after enabling preemption again,
+ * because even if the current thread is migrated to another CPU, reading
+ * the per-CPU value later will give us the same value as we update the
+ * per-CPU variable in the preempt notifier handlers.
  */
 struct kvm_vcpu *kvm_get_running_vcpu(void)
 {
-        return __this_cpu_read(kvm_running_vcpu);
+	struct kvm_vcpu *vcpu;
+
+	preempt_disable();
+	vcpu = __this_cpu_read(kvm_running_vcpu);
+	preempt_enable();
+
+	return vcpu;
 }
 
 /**