On 07/10/2013 05:49 PM, Alexander Graf wrote:
On 10.07.2013, at 08:02, Tiejun Chen wrote:We should ensure the preemption cannot occur while calling get_paca() insdide hard_irq_disable(), otherwise the paca_struct may be the wrong one just after. And btw, we may update timing stats in this case. Signed-off-by: Tiejun Chen <tiejun.c...@windriver.com> --- arch/powerpc/kvm/booke.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c index dcc94f0..9dae25d 100644 --- a/arch/powerpc/kvm/booke.c +++ b/arch/powerpc/kvm/booke.c @@ -839,6 +839,7 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu, WARN_ON(local_paca->irq_happened != 0); #endif + preempt_disable(); /* * We enter with interrupts disabled in hardware, but * we need to call hard_irq_disable anyway to ensure that @@ -848,6 +849,7 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu, /* update before a new last_exit_type is rewritten */ kvmppc_update_timing_stats(vcpu); + preempt_enable();All of the code here is already called with interrupts disabled. I don't see how we could preempt then?
But the kernel still check this in preempt case, #define get_paca() ((void) debug_smp_processor_id(), local_paca) then trigger that known call trace as I observed :) BUG: using smp_processor_id() in preemptible [00000000] code: qemu-system-ppc/2065 caller is .kvmppc_handle_exit+0x48/0x810 CPU: 0 PID: 2065 Comm: qemu-system-ppc Not tainted 3.10.0-172036-ge2daa28-dirty #116 Call Trace: [c0000001fc637570] [c00000000000835c] .show_stack+0x7c/0x1f0 (unreliable) [c0000001fc637640] [c000000000673a0c] .dump_stack+0x28/0x3c [c0000001fc6376b0] [c0000000002f04d8] .debug_smp_processor_id+0x108/0x120 [c0000001fc637740] [c0000000000444e8] .kvmppc_handle_exit+0x48/0x810 [c0000001fc6377f0] [c000000000047c80] .kvmppc_resume_host+0xa4/0xf8 Tiejun -- To unsubscribe from this list: send the line "unsubscribe kvm-ppc" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
