Re: [PATCH v5 10/12] Handle async PF in non preemptable context

[Avi Kivity]

 On 08/24/2010 12:36 PM, Gleb Natapov wrote:
> On Tue, Aug 24, 2010 at 12:30:25PM +0300, Avi Kivity wrote:
> >   On 07/19/2010 06:31 PM, Gleb Natapov wrote:
> > > If async page fault is received by idle task or when preemp_count is
> > > not zero guest cannot reschedule, so do sti; hlt and wait for page to be
> > > ready. vcpu can still process interrupts while it waits for the page to
> > > be ready.
> > >
> > > Acked-by: Rik van Riel<riel@xxxxxxxxxx>
> > > Signed-off-by: Gleb Natapov<gleb@xxxxxxxxxx>
> > > ---
> > >   arch/x86/kernel/kvm.c |   36 ++++++++++++++++++++++++++++++++----
> > >   1 files changed, 32 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
> > > index a6db92e..914b0fc 100644
> > > --- a/arch/x86/kernel/kvm.c
> > > +++ b/arch/x86/kernel/kvm.c
> > > @@ -37,6 +37,7 @@
> > >   #include<asm/cpu.h>
> > >   #include<asm/traps.h>
> > >   #include<asm/desc.h>
> > > +#include<asm/tlbflush.h>
> > >
> > >   #define MMU_QUEUE_SIZE 1024
> > >
> > > @@ -68,6 +69,8 @@ struct kvm_task_sleep_node {
> > >   	wait_queue_head_t wq;
> > >   	u32 token;
> > >   	int cpu;
> > > +	bool halted;
> > > +	struct mm_struct *mm;
> > >   };
> > >
> > >   static struct kvm_task_sleep_head {
> > > @@ -96,6 +99,11 @@ static void apf_task_wait(struct task_struct *tsk, u32 token)
> > >   	struct kvm_task_sleep_head *b =&async_pf_sleepers[key];
> > >   	struct kvm_task_sleep_node n, *e;
> > >   	DEFINE_WAIT(wait);
> > > +	int cpu, idle;
> > > +
> > > +	cpu = get_cpu();
> > > +	idle = idle_cpu(cpu);
> > > +	put_cpu();
> > >
> > >   	spin_lock(&b->lock);
> > >   	e = _find_apf_task(b, token);
> > > @@ -109,17 +117,31 @@ static void apf_task_wait(struct task_struct *tsk, u32 token)
> > >
> > >   	n.token = token;
> > >   	n.cpu = smp_processor_id();
> > > +	n.mm = current->active_mm;
> > > +	n.halted = idle || preempt_count()>   1;
> > > +	atomic_inc(&n.mm->mm_count);
> > >   	init_waitqueue_head(&n.wq);
> > >   	hlist_add_head(&n.link,&b->list);
> > >   	spin_unlock(&b->lock);
> > >
> > >   	for (;;) {
> > > -		prepare_to_wait(&n.wq,&wait, TASK_UNINTERRUPTIBLE);
> > > +		if (!n.halted)
> > > +			prepare_to_wait(&n.wq,&wait, TASK_UNINTERRUPTIBLE);
> > >   		if (hlist_unhashed(&n.link))
> > >   			break;
> > > -		schedule();
> > > +
> > > +		if (!n.halted) {
> > > +			schedule();
> > > +		} else {
> > > +			/*
> > > +			 * We cannot reschedule. So halt.
> > > +			 */
> > If we get the wakeup here, we'll halt and never wake up again.
> We will not. IRQs are disabled here. native_safe_halt() enables them.

Ok.

--
error compiling committee.c: too many arguments to function

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