Commit 83987ace authored Jan 08, 2013 by Christian Borntraeger Committed by Marcelo Tosatti Jan 10, 2013

s390/kvm: Fix BUG in include/linux/kvm_host.h:745



commit b080935c
    kvm: Directly account vtime to system on guest switch

also removed the irq_disable/enable around kvm guest switch, which
is correct in itself. Unfortunately, there is a BUG ON that (correctly)
checks for preemptible to cover the call to rcu later on.
(Introduced with commit 8fa22068
    KVM: make guest mode entry to be rcu quiescent state)

This check might trigger depending on the kernel config.
Lets make sure that no preemption happens during kvm_guest_enter.
We can enable preemption again after the call to
rcu_virt_note_context_switch returns.

Please note that we continue to run s390 guests with interrupts
enabled.

Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
CC: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

parent ecf02a60

arch/s390/kvm/kvm-s390.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -613,7 +613,9 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
		kvm_s390_deliver_pending_interrupts(vcpu);

		vcpu->arch.sie_block->icptcode = 0;
		preempt_disable();
		kvm_guest_enter();
		preempt_enable();
		VCPU_EVENT(vcpu, 6, "entering sie flags %x",
		atomic_read(&vcpu->arch.sie_block->cpuflags));
		trace_kvm_s390_sie_enter(vcpu,

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