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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: Scott Wood <scottwood@freescale.com>
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Alexander Graf 2011-12-19 13:36:55 +01:00 committed by Avi Kivity
parent ae21216bec
commit e371f713db
1 changed files with 20 additions and 0 deletions
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20
arch/powerpc/kvm/book3s_pr.c
View File

@ -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 @@ program_interrupt:
/* 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;