Re: [PATCH RFC v2 1/4] Introduce kvm_vcpu_is_bsp() function.

[Gleb Natapov <gleb@redhat.com>]

On Mon, May 25, 2009 at 05:46:22PM -0300, Marcelo Tosatti wrote:
> On Mon, May 25, 2009 at 06:50:33PM +0300, Gleb Natapov wrote:
> > Use it instead of open code "vcpu_id zero is BSP" assumption.
> > 
> > Signed-off-by: Gleb Natapov <gleb@redhat.com>
> > ---
> >  arch/ia64/kvm/kvm-ia64.c |    2 +-
> >  arch/ia64/kvm/vcpu.c     |    2 +-
> >  arch/x86/kvm/i8254.c     |    4 ++--
> >  arch/x86/kvm/i8259.c     |    6 +++---
> >  arch/x86/kvm/lapic.c     |    7 ++++---
> >  arch/x86/kvm/svm.c       |    4 ++--
> >  arch/x86/kvm/vmx.c       |    6 +++---
> >  arch/x86/kvm/x86.c       |    4 ++--
> >  include/linux/kvm_host.h |    5 +++++
> >  virt/kvm/ioapic.c        |    4 +++-
> >  virt/kvm/kvm_main.c      |    2 ++
> >  11 files changed, 28 insertions(+), 18 deletions(-)
> > 
> >  #endif
> > diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
> > index 1eddae9..a8a8252 100644
> > --- a/virt/kvm/ioapic.c
> > +++ b/virt/kvm/ioapic.c
> > @@ -165,7 +165,9 @@ static int ioapic_deliver(struct kvm_ioapic *ioapic, int irq)
> >  	/* Always delivery PIT interrupt to vcpu 0 */
> >  	if (irq == 0) {
> >  		irqe.dest_mode = 0; /* Physical mode. */
> > -		irqe.dest_id = ioapic->kvm->vcpus[0]->vcpu_id;
> > +		/* need to read apic_id from apic regiest since
> > +		 * it can be rewritten */
> > +		irqe.dest_id = ioapic->kvm->bsp_vcpu->vcpu_id;
> >  	}
> 
> Won't this oops if userspace creates only vcpu 3 and attempts to deliver
> to IRQ0 ? (not directly related to the patchset though).
I doesn't oops since if BSP is not created this code is not reached
(nothing runs eventually). But see below.

> 
> Also you said "The code still assumes that boot cpu is created first."
> Where is that?
> 
Oops. It should be like this, but this patch series has a bug. In
 kvm_vm_ioctl_create_vcpu:
	if (id == 0)
		kvm->bsp_vcpu = vcpu;
should be:
	if (!kvm->bsp_vcpu)
		kvm->bsp_vcpu = vcpu;

I really don't want to make acpi_id zero to be special.
 
> Otherwise, neat!
> 
> >  #endif
> >  	return kvm_irq_delivery_to_apic(ioapic->kvm, NULL, &irqe);
> > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> > index de042cb..5a55fe0 100644
> > --- a/virt/kvm/kvm_main.c
> > +++ b/virt/kvm/kvm_main.c
> > @@ -1737,6 +1737,8 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, int n)
> >  		goto vcpu_destroy;
> >  	}
> >  	kvm->vcpus[n] = vcpu;
> > +	if (n == 0)
> > +		kvm->bsp_vcpu = vcpu;
> >  	mutex_unlock(&kvm->lock);
> >  
> >  	/* Now it's all set up, let userspace reach it */
> > -- 
> > 1.6.2.1
> > 
> > --
> > To unsubscribe from this list: send the line "unsubscribe kvm" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html

--
			Gleb.