Re: [PATCH v5 19/23] KVM: arm64: GICv4.1: Allow SGIs to switch between HW and SW interrupts

[Marc Zyngier]

Hi Eric,

On 2020-03-19 16:16, Auger Eric wrote:
> Hi Marc,
>
> On 3/4/20 9:33 PM, Marc Zyngier wrote:
> > In order to let a guest buy in the new, active-less SGIs, we
> > need to be able to switch between the two modes.
> >
> > Handle this by stopping all guest activity, transfer the state
> > from one mode to the other, and resume the guest. Nothing calls
> > this code so far, but a later patch will plug it into the MMIO
> > emulation.
> >
> > Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
> > ---
> >  include/kvm/arm_vgic.h      |  3 ++
> >  virt/kvm/arm/vgic/vgic-v4.c | 94 
> > +++++++++++++++++++++++++++++++++++++
> >  virt/kvm/arm/vgic/vgic.h    |  1 +
> >  3 files changed, 98 insertions(+)
> >
> > diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
> > index 63457908c9c4..69f4164d6477 100644
> > --- a/include/kvm/arm_vgic.h
> > +++ b/include/kvm/arm_vgic.h
> > @@ -231,6 +231,9 @@ struct vgic_dist {
> >  	/* distributor enabled */
> >  	bool			enabled;
> >
> > +	/* Wants SGIs without active state */
> > +	bool			nassgireq;
> > +
> >  	struct vgic_irq		*spis;
> >
> >  	struct vgic_io_device	dist_iodev;
> > diff --git a/virt/kvm/arm/vgic/vgic-v4.c b/virt/kvm/arm/vgic/vgic-v4.c
> > index c2fcde104ea2..a65dc1c85363 100644
> > --- a/virt/kvm/arm/vgic/vgic-v4.c
> > +++ b/virt/kvm/arm/vgic/vgic-v4.c
> > @@ -97,6 +97,100 @@ static irqreturn_t vgic_v4_doorbell_handler(int 
> > irq, void *info)
> >  	return IRQ_HANDLED;
> >  }
> >
> > +static void vgic_v4_sync_sgi_config(struct its_vpe *vpe, struct 
> > vgic_irq *irq)
> > +{
> > +	vpe->sgi_config[irq->intid].enabled	= irq->enabled;
> > +	vpe->sgi_config[irq->intid].group 	= irq->group;
> > +	vpe->sgi_config[irq->intid].priority	= irq->priority;
> > +}
> > +
> > +static void vgic_v4_enable_vsgis(struct kvm_vcpu *vcpu)
> > +{
> > +	struct its_vpe *vpe = &vcpu->arch.vgic_cpu.vgic_v3.its_vpe;
> > +	int i;
> > +
> > +	/*
> > +	 * With GICv4.1, every virtual SGI can be directly injected. So
> > +	 * let's pretend that they are HW interrupts, tied to a host
> > +	 * IRQ. The SGI code will do its magic.
> > +	 */
> > +	for (i = 0; i < VGIC_NR_SGIS; i++) {
> > +		struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, i);
> > +		struct irq_desc *desc;
> > +		int ret;
> Is is safe without holding the irq->irq_lock?

The assumption here is that we're coming vgic_v4_configure_vsgis(), 
which starts
by stopping the whole guest. My guess is that it should be safe enough, 
but
maybe you are thinking of something else?

Thanks,

         M.
--
Jazz is not dead. It just smells funny...