KVM: ia64: fix locking order entering guest

Reorder locking as down_read() may return with local interrupts enabled,
which means we could go into vti_vcpu_run() with interrupts enabled.

This caused random crashes on the Altix as the timer interrupt tried
to read a memory mapped clock source, for which the TLB had not yet been
reinstated in the exit, before ipsr was retored.

Signed-off-by: Jes Sorensen <jes@sgi.com>
Acked-by: Xiantao Zhang <xiantao.zhang@intel.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 8 insertions, 6 deletions

diff --git a/arch/ia64/kvm/kvm-ia64.c b/arch/ia64/kvm/kvm-ia64.c
index 28af6a731bb8..d20a5db4c4dd 100644
--- a/arch/ia64/kvm/kvm-ia64.c
+++ b/arch/ia64/kvm/kvm-ia64.c
@@ -610,20 +610,22 @@ static int __vcpu_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
         int r;
 
 again:
-        preempt_disable();
-        local_irq_disable();
-
         if (signal_pending(current)) {
-                local_irq_enable();
-                preempt_enable();
                 r = -EINTR;
                 kvm_run->exit_reason = KVM_EXIT_INTR;
                 goto out;
         }
 
+        /*
+         * down_read() may sleep and return with interrupts enabled
+         */
+        down_read(&vcpu->kvm->slots_lock);
+
+        preempt_disable();
+        local_irq_disable();
+
         vcpu->guest_mode = 1;
         kvm_guest_enter();
-        down_read(&vcpu->kvm->slots_lock);
         r = vti_vcpu_run(vcpu, kvm_run);
         if (r < 0) {
                 local_irq_enable();