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Re: [PATCH v3 51/59] KVM: arm/arm64: GICv4: Add doorbell interrupt handling

From Marc Zyngier <marc.zyngier@arm.com>
Newsgroups linux.kernel
Subject Re: [PATCH v3 51/59] KVM: arm/arm64: GICv4: Add doorbell interrupt handling
Date 2017-08-04 09:50 +0200
Message-ID <uaFwR-47W-7@gated-at.bofh.it> (permalink)
References <u9mFX-DO-3@gated-at.bofh.it> <u9mPE-H2-29@gated-at.bofh.it>
Organization ARM Ltd

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On 31/07/17 18:26, Marc Zyngier wrote:
> When a vPE is not running, a VLPI being made pending results in a
> doorbell interrupt being delivered. Let's handle this interrupt
> and update the pending_last flag that indicates that VLPIs are
> pending. The corresponding vcpu is also kicked into action.
> 
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> ---
>  virt/kvm/arm/vgic/vgic-v4.c | 34 ++++++++++++++++++++++++++++++++++
>  1 file changed, 34 insertions(+)
> 
> diff --git a/virt/kvm/arm/vgic/vgic-v4.c b/virt/kvm/arm/vgic/vgic-v4.c
> index 534d3051a078..6af3cde6d7d4 100644
> --- a/virt/kvm/arm/vgic/vgic-v4.c
> +++ b/virt/kvm/arm/vgic/vgic-v4.c
> @@ -21,6 +21,19 @@
>  
>  #include "vgic.h"
>  
> +static irqreturn_t vgic_v4_doorbell_handler(int irq, void *info)
> +{
> +	struct kvm_vcpu *vcpu = info;
> +
> +	if (!kvm_vgic_vcpu_pending_irq(vcpu)) {
> +		vcpu->arch.vgic_cpu.vgic_v3.its_vpe.pending_last = true;
> +		kvm_make_request(KVM_REQ_IRQ_PENDING, vcpu);
> +		kvm_vcpu_kick(vcpu);
> +	}

This code is so obviously broken that I completely overlooked it.

If we have take a doorbell interrupt, then it means nothing was
otherwise pending (because we'd have been kicked out of the blocking
state, and will have masked the doorbell). So checking for pending
interrupts is pointless.

Furthermore, calling kvm_vgic_vcpu_pending_irq() takes the ap_list
lock. If we take a doorbell interrupt while injecting a virtual
interrupt (from userspace, for example) on the same CPU, we end-up
in deadlock land. This would be solved by Christoffer's latest
crop of timer patches, but there is no point getting there the first
place.

The patchlet below solves it:

diff --git a/virt/kvm/arm/vgic/vgic-v4.c b/virt/kvm/arm/vgic/vgic-v4.c
index 15feb1151797..48e4d6ebeaa8 100644
--- a/virt/kvm/arm/vgic/vgic-v4.c
+++ b/virt/kvm/arm/vgic/vgic-v4.c
@@ -94,11 +94,9 @@ static irqreturn_t vgic_v4_doorbell_handler(int irq, void *info)
 {
 	struct kvm_vcpu *vcpu = info;
 
-	if (!kvm_vgic_vcpu_pending_irq(vcpu)) {
-		vcpu->arch.vgic_cpu.vgic_v3.its_vpe.pending_last = true;
-		kvm_make_request(KVM_REQ_IRQ_PENDING, vcpu);
-		kvm_vcpu_kick(vcpu);
-	}
+	vcpu->arch.vgic_cpu.vgic_v3.its_vpe.pending_last = true;
+	kvm_make_request(KVM_REQ_IRQ_PENDING, vcpu);
+	kvm_vcpu_kick(vcpu);
 
 	return IRQ_HANDLED;
 }

and I've queued it for the next round.

Thanks,

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

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[PATCH v3 00/59] irqchip: KVM: Add support for GICv4 Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 19:30 +0200
  [PATCH v3 10/59] irqchip/gic-v3-its: Split out pending table allocation Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 19:30 +0200
  [PATCH v3 37/59] KVM: arm/arm64: vgic: Move kvm_vgic_destroy call around Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 19:30 +0200
  [PATCH v3 12/59] irqchip/gic-v3-its: Generalize device table allocation Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 19:30 +0200
  [PATCH v3 55/59] KVM: arm/arm64: GICv4: Enable VLPI support Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 19:30 +0200
  [PATCH v3 14/59] irqchip/gic-v4: Add management structure definitions Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 19:30 +0200
  [PATCH v3 54/59] KVM: arm/arm64: GICv4: Enable virtual cpuif if VLPIs can be delivered Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 19:30 +0200
  [PATCH v3 45/59] KVM: arm/arm64: GICv4: Handle CLEAR applied to a VLPI Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 19:30 +0200
  [PATCH v3 49/59] KVM: arm/arm64: GICv4: Propagate VLPI properties at map time Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 19:30 +0200
  [PATCH v3 59/59] irqchip/gic-v3-its: Workaround Huawei D05 redistributor addressing Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 19:30 +0200
  [PATCH v3 47/59] KVM: arm/arm64: GICv4: Propagate property updates to VLPIs Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 19:30 +0200
  [PATCH v3 05/59] irqchip/gic-v3-its: Add probing for VLPI properties Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 19:30 +0200
  [PATCH v3 29/59] irqchip/gic-v3-its: Set implementation defined bit to enable VLPIs Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 19:30 +0200
  [PATCH v3 33/59] irqchip/gic-v4: Add some basic documentation Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 19:30 +0200
  [PATCH v3 35/59] irqchip/gic-v3: Advertise GICv4 support to KVM Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 19:30 +0200
  [PATCH v3 41/59] KVM: arm/arm64: GICv4: Wire mapping/unmapping of VLPIs in VFIO irq bypass Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 19:30 +0200
  [PATCH v3 58/59] irqchip/gic-v3-its: Pass its_node pointer to each command bulder Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 19:30 +0200
  [PATCH v3 39/59] KVM: arm/arm64: GICv4: Add property field and per-VM predicate Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 19:30 +0200
  [PATCH v3 43/59] KVM: arm/arm64: GICv4: Unmap VLPI when freeing an LPI Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 19:30 +0200
  [PATCH v3 31/59] irqchip/gic-v4: Add VPE command interface Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 19:30 +0200
  [PATCH v3 24/59] irqchip/gic-v3-its: Add VPE invalidation hook Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 19:30 +0200
  [PATCH v3 19/59] irqchip/gic-v3-its: Add VPE domain infrastructure Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 19:30 +0200
  [PATCH v3 40/59] KVM: arm/arm64: GICv4: Add init/teardown of the per-VM vPE irq domain Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 19:30 +0200
  [PATCH v3 52/59] KVM: arm/arm64: GICv4: Use the doorbell interrupt as an unblocking source Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 19:40 +0200
  [PATCH v3 53/59] KVM: arm/arm64: GICv4: Hook vPE scheduling into vgic flush/sync Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 19:40 +0200
  [PATCH v3 44/59] KVM: arm/arm64: GICv4: Handle MOVI applied to a VLPI Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 19:40 +0200
  [PATCH v3 48/59] KVM: arm/arm64: GICv4: Handle INVALL applied to a vPE Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 19:40 +0200
  [PATCH v3 51/59] KVM: arm/arm64: GICv4: Add doorbell interrupt handling Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 19:40 +0200
    Re: [PATCH v3 51/59] KVM: arm/arm64: GICv4: Add doorbell interrupt  handling Marc Zyngier <marc.zyngier@arm.com> - 2017-08-04 09:50 +0200
  [PATCH v3 42/59] KVM: arm/arm64: GICv4: Handle INT command applied to a VLPI Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 19:40 +0200
  [PATCH v3 46/59] KVM: arm/arm64: GICv4: Handle MOVALL applied to a vPE Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 19:40 +0200
  [PATCH v3 56/59] KVM: arm/arm64: GICv4: Prevent heterogenous systems from using GICv4 Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 19:40 +0200
  [PATCH v3 50/59] KVM: arm/arm64: GICv4: Use pending_last as a scheduling hint Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 19:40 +0200
  [PATCH v3 57/59] KVM: arm/arm64: GICv4: Theory of operations Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 19:40 +0200
  [PATCH v3 38/59] KVM: arm/arm64: vITS: Add MSI translation helpers Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 20:00 +0200
  [PATCH v3 32/59] irqchip/gic-v4: Add VLPI configuration interface Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 20:00 +0200
  [PATCH v3 08/59] irqchip/gic-v3-its: Split out property table allocation Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 20:00 +0200
  [PATCH v3 30/59] irqchip/gic-v4: Add per-VM VPE domain creation Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 20:00 +0200
  [PATCH v3 36/59] KVM: arm: Select ARM_GIC_V3 and ARM_GIC_V3_ITS Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 20:00 +0200
  [PATCH v3 09/59] irqchip/gic-v3-its: Allow use of indirect VCPU tables Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 20:00 +0200
  [PATCH v3 13/59] irqchip/gic-v3-its: Generalize LPI configuration Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 20:00 +0200
  [PATCH v3 34/59] irqchip/gic-v4: Enable low-level GICv4 operations Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 20:00 +0200
  [PATCH v3 22/59] irqchip/gic-v3-its: Add VPENDBASER/VPROPBASER accessors Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 20:00 +0200
  [PATCH v3 15/59] irqchip/gic-v3-its: Add GICv4 ITS command definitions Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 20:00 +0200
  [PATCH v3 27/59] irqchip/gic-v3-its: Support VPE doorbell invalidation even when !DirectLPI Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 20:00 +0200
  [PATCH v3 26/59] irqchip/gic-v3-its: Add VPE interrupt masking Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 20:00 +0200
  [PATCH v3 16/59] irqchip/gic-v3-its: Add VLPI configuration hook Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 20:00 +0200
  [PATCH v3 28/59] irqchip/gic-v3-its: Allow doorbell interrupts to be injected/cleared Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 20:00 +0200
  [PATCH v3 06/59] irqchip/gic-v3-its: Macro-ize its_send_single_command Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 20:00 +0200
  [PATCH v3 25/59] irqchip/gic-v3-its: Add VPE affinity changes Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 20:00 +0200
  [PATCH v3 17/59] irqchip/gic-v3-its: Add VLPI map/unmap operations Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 20:00 +0200
  [PATCH v3 11/59] irqchip/gic-v3-its: Rework LPI freeing Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 20:00 +0200
  [PATCH v3 20/59] irqchip/gic-v3-its: Add VPE irq domain allocation/teardown Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 20:00 +0200
  [PATCH v3 18/59] irqchip/gic-v3-its: Add VLPI configuration handling Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 20:00 +0200
  [PATCH v3 23/59] irqchip/gic-v3-its: Add VPE scheduling Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 20:00 +0200
  [PATCH v3 02/59] irqchip/gic-v3: Add redistributor iterator Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 20:10 +0200
  [PATCH v3 01/59] genirq: Let irq_set_vcpu_affinity() iterate over hierarchy Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 20:10 +0200
  [PATCH v3 07/59] irqchip/gic-v3-its: Implement irq_set_irqchip_state for pending state Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 20:10 +0200
  [PATCH v3 03/59] irqchip/gic-v3: Add VLPI/DirectLPI discovery Marc Zyngier <marc.zyngier@arm.com> - 2017-07-31 20:10 +0200

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