Re: [RFC v2 06/10] KVM: arm/arm64: Update the physical timer interrupt level

From: Christoffer Dall <christoffer.dall@linaro.org>
To: Jintack Lim <jintack@cs.columbia.edu>
Cc: "Marc Zyngier" <marc.zyngier@arm.com>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"Radim Krčmář" <rkrcmar@redhat.com>,
	linux@armlinux.org.uk,
	"Catalin Marinas" <catalin.marinas@arm.com>,
	"Will Deacon" <will.deacon@arm.com>,
	"Andre Przywara" <andre.przywara@arm.com>,
	"KVM General" <kvm@vger.kernel.org>,
	arm-mail-list <linux-arm-kernel@lists.infradead.org>,
	kvmarm@lists.cs.columbia.edu,
	"lkml - Kernel Mailing List" <linux-kernel@vger.kernel.org>
Subject: Re: [RFC v2 06/10] KVM: arm/arm64: Update the physical timer interrupt level
Date: Wed, 1 Feb 2017 11:07:16 +0100	[thread overview]
Message-ID: <20170201100716.GC6226@cbox> (raw)
In-Reply-To: <CAHyh4xjTWK0HeQhX9X6+6Ez706Sh4+=3wMq0b9rmvGTbD8q80g@mail.gmail.com>

On Wed, Feb 01, 2017 at 03:40:10AM -0500, Jintack Lim wrote:
> On Wed, Feb 1, 2017 at 3:04 AM, Christoffer Dall
> <christoffer.dall@linaro.org> wrote:
> > On Sun, Jan 29, 2017 at 03:21:06PM +0000, Marc Zyngier wrote:
> >> On Fri, Jan 27 2017 at 01:04:56 AM, Jintack Lim <jintack@cs.columbia.edu> wrote:
> >> > Now that we maintain the EL1 physical timer register states of VMs,
> >> > update the physical timer interrupt level along with the virtual one.
> >> >
> >> > Note that the emulated EL1 physical timer is not mapped to any hardware
> >> > timer, so we call a proper vgic function.
> >> >
> >> > Signed-off-by: Jintack Lim <jintack@cs.columbia.edu>
> >> > ---
> >> >  virt/kvm/arm/arch_timer.c | 20 ++++++++++++++++++++
> >> >  1 file changed, 20 insertions(+)
> >> >
> >> > diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
> >> > index 0f6e935..3b6bd50 100644
> >> > --- a/virt/kvm/arm/arch_timer.c
> >> > +++ b/virt/kvm/arm/arch_timer.c
> >> > @@ -180,6 +180,21 @@ static void kvm_timer_update_mapped_irq(struct kvm_vcpu *vcpu, bool new_level,
> >> >     WARN_ON(ret);
> >> >  }
> >> >
> >> > +static void kvm_timer_update_irq(struct kvm_vcpu *vcpu, bool new_level,
> >> > +                            struct arch_timer_context *timer)
> >> > +{
> >> > +   int ret;
> >> > +
> >> > +   BUG_ON(!vgic_initialized(vcpu->kvm));
> >>
> >> Although I've added my fair share of BUG_ON() in the code base, I've
> >> since reconsidered my position. If we get in a situation where the vgic
> >> is not initialized, maybe it would be better to just WARN_ON and return
> >> early rather than killing the whole box. Thoughts?
> >>
> >
> > Could we help this series along by saying that since this BUG_ON already
> > exists in the kvm_timer_update_mapped_irq function, then it just
> > preserves functionality and it's up to someone else (me) to remove the
> > BUG_ON from both functions later in life?
> >
> 
> Sounds good to me :) Thanks!
> 

So just as you thought you were getting off easy...

The reason we now have kvm_timer_update_irq and
kvm_timer_update_mapped_irq is that we have the following two vgic
functions:

kvm_vgic_inject_irq
kvm_vgic_inject_mapped_irq

But the only difference between the two is what they pass
as the mapped_irq argument to vgic_update_irq_pending.

What about if we just had this as a precursor patch:

diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
index 6a084cd..91ecf48 100644
--- a/virt/kvm/arm/arch_timer.c
+++ b/virt/kvm/arm/arch_timer.c
@@ -175,7 +175,8 @@ static void kvm_timer_update_irq(struct kvm_vcpu *vcpu, bool new_level)
 	timer->irq.level = new_level;
 	trace_kvm_timer_update_irq(vcpu->vcpu_id, timer->irq.irq,
 				   timer->irq.level);
-	ret = kvm_vgic_inject_mapped_irq(vcpu->kvm, vcpu->vcpu_id,
+
+	ret = kvm_vgic_inject_irq(vcpu->kvm, vcpu->vcpu_id,
 					 timer->irq.irq,
 					 timer->irq.level);
 	WARN_ON(ret);
diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
index dea12df..4c87fd0 100644
--- a/virt/kvm/arm/vgic/vgic.c
+++ b/virt/kvm/arm/vgic/vgic.c
@@ -336,8 +336,7 @@ bool vgic_queue_irq_unlock(struct kvm *kvm, struct vgic_irq *irq)
 }
 
 static int vgic_update_irq_pending(struct kvm *kvm, int cpuid,
-				   unsigned int intid, bool level,
-				   bool mapped_irq)
+				   unsigned int intid, bool level)
 {
 	struct kvm_vcpu *vcpu;
 	struct vgic_irq *irq;
@@ -357,11 +356,6 @@ static int vgic_update_irq_pending(struct kvm *kvm, int cpuid,
 	if (!irq)
 		return -EINVAL;
 
-	if (irq->hw != mapped_irq) {
-		vgic_put_irq(kvm, irq);
-		return -EINVAL;
-	}
-
 	spin_lock(&irq->irq_lock);
 
 	if (!vgic_validate_injection(irq, level)) {
@@ -399,13 +393,7 @@ static int vgic_update_irq_pending(struct kvm *kvm, int cpuid,
 int kvm_vgic_inject_irq(struct kvm *kvm, int cpuid, unsigned int intid,
 			bool level)
 {
-	return vgic_update_irq_pending(kvm, cpuid, intid, level, false);
-}
-
-int kvm_vgic_inject_mapped_irq(struct kvm *kvm, int cpuid, unsigned int intid,
-			       bool level)
-{
-	return vgic_update_irq_pending(kvm, cpuid, intid, level, true);
+	return vgic_update_irq_pending(kvm, cpuid, intid, level);
 }
 
 int kvm_vgic_map_phys_irq(struct kvm_vcpu *vcpu, u32 virt_irq, u32 phys_irq)


That would make this patch simpler.  If so, I can send out the above
patch with a proper description.

Thanks,
-Christoffer
