On Wed, Apr 04, 2012 at 07:04:16AM -0700, Paul E. McKenney wrote: > On Wed, Apr 04, 2012 at 03:30:33PM +0300, Gleb Natapov wrote: > > On Tue, Apr 03, 2012 at 01:52:26PM +0300, Gleb Natapov wrote: > > > On Mon, Apr 02, 2012 at 08:54:32PM -0400, Sasha Levin wrote: > > > > Hi all, > > > > > > > > I got the spew at the bottom of the mail in a KVM guest using the KVM tools and running trinity. > > > > > > > > I'm not quite sure how default_idle managed to trigger a pagefault, so that part looks odd to me. > > > > > > > This is not regular page fault. This is async page fault that tells the > > > guest that a page, previously swapped out by hypervisor, is now swapped > > > back in and it can happen while vcpu is idle. The code does not leave > > > idle state properly though. We probably need to call rcu_irq_enter() > > > there. Will look into it. > > > > > > > The patch below solves it for me: > > > > "Page ready" async PF can kick vcpu out of idle state much like IRQ. > > We need to tell RCU about this. > > This is invoked from an exception or interrupt handler, not from > process-level code? If so: > >From an exception. > Reviewed-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> > > > Signed-off-by: Gleb Natapov <gleb@xxxxxxxxxx> > > diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c > > index f0c6fd6..380079f 100644 > > --- a/arch/x86/kernel/kvm.c > > +++ b/arch/x86/kernel/kvm.c > > @@ -38,6 +38,7 @@ > > #include <asm/traps.h> > > #include <asm/desc.h> > > #include <asm/tlbflush.h> > > +#include <asm/idle.h> > > > > static int kvmapf = 1; > > > > @@ -253,7 +254,10 @@ do_async_page_fault(struct pt_regs *regs, unsigned long error_code) > > kvm_async_pf_task_wait((u32)read_cr2()); > > break; > > case KVM_PV_REASON_PAGE_READY: > > + rcu_irq_enter(); > > + exit_idle(); > > kvm_async_pf_task_wake((u32)read_cr2()); > > + rcu_irq_exit(); > > break; > > } > > } > > -- > > Gleb. > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- Gleb. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
