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Commit e371f713 authored by Alexander Graf's avatar Alexander Graf Committed by Avi Kivity
Browse files

KVM: PPC: Book3S: PR: Fix signal check race 



As Scott put it:

> If we get a signal after the check, we want to be sure that we don't
> receive the reschedule IPI until after we're in the guest, so that it
> will cause another signal check.

we need to have interrupts disabled from the point we do signal_check()
all the way until we actually enter the guest.

This patch fixes potential signal loss races.

Reported-by: default avatarScott Wood <scottwood@freescale.com>
Signed-off-by: default avatarAlexander Graf <agraf@suse.de>
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent ae21216b

arch/powerpc/kvm/book3s_pr.c

+20 −0
Original line number Diff line number Diff line
@@ -51,6 +51,8 @@ static int kvmppc_handle_ext(struct kvm_vcpu *vcpu, unsigned int exit_nr, 
#define MSR_USER32 MSR_USER

#define MSR_USER64 MSR_USER

#define HW_PAGE_SIZE PAGE_SIZE

#define __hard_irq_disable local_irq_disable

#define __hard_irq_enable local_irq_enable

#endif



void kvmppc_core_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
@@ -776,7 +778,16 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu, 
		/* To avoid clobbering exit_reason, only check for signals if

		 * we aren't already exiting to userspace for some other

		 * reason. */



		/*

		 * Interrupts could be timers for the guest which we have to

		 * inject again, so let's postpone them until we're in the guest

		 * and if we really did time things so badly, then we just exit

		 * again due to a host external interrupt.

		 */

		__hard_irq_disable();

		if (signal_pending(current)) {

			__hard_irq_enable();

#ifdef EXIT_DEBUG

			printk(KERN_EMERG "KVM: Going back to host\n");

#endif
@@ -959,8 +970,17 @@ int kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu *vcpu) 


	kvmppc_core_prepare_to_enter(vcpu);



	/*

	 * Interrupts could be timers for the guest which we have to inject

	 * again, so let's postpone them until we're in the guest and if we

	 * really did time things so badly, then we just exit again due to

	 * a host external interrupt.

	 */

	__hard_irq_disable();



	/* No need to go into the guest when all we do is going out */

	if (signal_pending(current)) {

		__hard_irq_enable();

		kvm_run->exit_reason = KVM_EXIT_INTR;

		ret = -EINTR;

		goto out;