Re: [PATCH] Fix block mode during halt emulation

[Marcelo Tosatti <mtosatti@redhat.com>]

Hi Dor,

On Tue, Jul 01, 2008 at 01:30:08AM +0300, Dor Laor wrote:
> >From d85feaae019bc0abc98a2524369e04d521a78aa8 Mon Sep 17 00:00:00 2001
> From: Dor Laor <dor.laor@qumranet.com>
> Date: Mon, 30 Jun 2008 18:22:44 -0400
> Subject: [PATCH] Fix block mode hduring halt emulation
> 
> There is no need to check for pending pit/apic timer, nor
> pending virq, since all of the check KVM_MP_STATE_RUNNABLE
> and wakeup the waitqueue.
> 
> It fixes 100% cpu when windows guest is shutdown (non acpi HAL)

You need to test for pending interrupts and timers. IRQ injection and
timers can trigger before kvm_vcpu_block() adds the running thread to
the waitqueue, in which case waitqueue_active() test fails.

> Signed-off-by: Dor Laor <dor.laor@qumranet.com>
> ---
>  virt/kvm/kvm_main.c |    4 ----
>  1 files changed, 0 insertions(+), 4 deletions(-)
> 
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index b90da0b..faa0778 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -816,10 +816,6 @@ void kvm_vcpu_block(struct kvm_vcpu *vcpu)
>  	for (;;) {
>  		prepare_to_wait(&vcpu->wq, &wait, TASK_INTERRUPTIBLE);
>  
> -		if (kvm_cpu_has_interrupt(vcpu))
> -			break;
> -		if (kvm_cpu_has_pending_timer(vcpu))
> -			break;
>  		if (kvm_arch_vcpu_runnable(vcpu))
>  			break;
>  		if (signal_pending(current))
> -- 
> 1.5.4