Zhang, Xiantao wrote:
Yeah, that is very strange! I will check it tomorrow, and have to sleep now :-)
Xiantao
Hi Xiantao,
I think I got it!
We were calling local_irqs_disable() before calling down_read(), but
down_read() can sleep and so may return with local interrupts
re-enabled.....
I have reordered things so now we should be safe.
How does this patch look to you?
Cheers,
Jes
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@xxxxxxx>
---
arch/ia64/kvm/kvm-ia64.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
Index: linux-2.6.git/arch/ia64/kvm/kvm-ia64.c
===================================================================
--- linux-2.6.git.orig/arch/ia64/kvm/kvm-ia64.c
+++ linux-2.6.git/arch/ia64/kvm/kvm-ia64.c
@@ -610,20 +610,22 @@
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();
