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From: Marc Zyngier <maz@kernel.org>
To: Shaokun Zhang <zhangshaokun@hisilicon.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	Jason Cooper <jason@lakedaemon.net>,
	linux-kernel@vger.kernel.org,
	Robert Richter <rrichter@marvell.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	kvmarm@lists.cs.columbia.edu
Subject: Re: [PATCH v3 29/32] KVM: arm64: GICv4.1: Allow SGIs to switch between HW and SW interrupts
Date: Wed, 15 Jan 2020 13:17:24 +0000
Message-ID: <c5d057291e01a1d0b02290504f8ed048@kernel.org> (raw)
In-Reply-To: <cc5fe20c-7a0c-c266-e78a-2a85963ab20f@hisilicon.com>

On 2020-01-15 02:49, Shaokun Zhang wrote:
> Hi Marc, [This is from Nianyao]
> 
> On 2019/12/24 19:10, 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.
>> 
>> Signed-off-by: Marc Zyngier <maz@kernel.org>
>> ---
>>  include/kvm/arm_vgic.h      |  3 ++
>>  virt/kvm/arm/vgic/vgic-v3.c |  2 +
>>  virt/kvm/arm/vgic/vgic-v4.c | 96 
>> +++++++++++++++++++++++++++++++++++++
>>  virt/kvm/arm/vgic/vgic.h    |  1 +
>>  4 files changed, 102 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-v3.c b/virt/kvm/arm/vgic/vgic-v3.c
>> index c2fdea201747..c79a251c4974 100644
>> --- a/virt/kvm/arm/vgic/vgic-v3.c
>> +++ b/virt/kvm/arm/vgic/vgic-v3.c
>> @@ -540,6 +540,8 @@ int vgic_v3_map_resources(struct kvm *kvm)
>>  		goto out;
>>  	}
>> 
>> +	if (kvm_vgic_global_state.has_gicv4_1)
>> +		vgic_v4_configure_vsgis(kvm);
>>  	dist->ready = true;
>> 
>>  out:
>> diff --git a/virt/kvm/arm/vgic/vgic-v4.c b/virt/kvm/arm/vgic/vgic-v4.c
>> index c2fcde104ea2..063785fd2dc7 100644
>> --- a/virt/kvm/arm/vgic/vgic-v4.c
>> +++ b/virt/kvm/arm/vgic/vgic-v4.c
>> @@ -97,6 +97,102 @@ 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;
>> +
>> +		if (irq->hw) {
>> +			vgic_put_irq(vcpu->kvm, irq);
>> +			continue;
>> +		}
>> +
>> +		irq->hw = true;
>> +		irq->host_irq = irq_find_mapping(vpe->sgi_domain, i);
> 
> I think we need to check whether irq_find_mapping returns 0.

Why? its_alloc_vcpu_sgis() performs the allocation of all 16 SGIs
in one go. If that fails, we should error out. Conversely, we're
guaranteed that we have a mapping if it hasn't failed.

> 
>> +		vgic_v4_sync_sgi_config(vpe, irq);
>> +		/*
>> +		 * SGIs are initialised as disabled. Enable them if
>> +		 * required by the rest of the VGIC init code.
>> +		 */
>> +		desc = irq_to_desc(irq->host_irq);
>> +		ret = irq_domain_activate_irq(irq_desc_get_irq_data(desc),
>> +					      false);
> 
> If irq->host_irq is not valid , in irq_domain_activate_irq, it will
> trigger NULL pointer dereference in host kernel.
> I meet a problem here. When hw support GIC4.1, and host kernel is 
> started with
> kvm-arm.vgic_v4_enable=0, starting a virtual machine will trigger NULL 
> pointer
> dereference in host. The following is error info:

[...]

But the problem here is that we're trying to use GICv4.1 even if GICv4
is disabled. I don't think there is a point in trying to sidestep this
locally if we're doing the wrong thing at top-level, which seems to be
the case.

Thanks,

         M.
-- 
Jazz is not dead. It just smells funny...
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  parent reply index

Thread overview: 53+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-24 11:10 [PATCH v3 00/32] irqchip/gic-v4: GICv4.1 architecture support Marc Zyngier
2019-12-24 11:10 ` [PATCH v3 01/32] irqchip/gic-v3: Detect GICv4.1 supporting RVPEID Marc Zyngier
2019-12-24 11:10 ` [PATCH v3 02/32] irqchip/gic-v3: Add GICv4.1 VPEID size discovery Marc Zyngier
2019-12-24 11:10 ` [PATCH v3 03/32] irqchip/gic-v3: Workaround Cavium TX1 erratum when reading GICD_TYPER2 Marc Zyngier
2020-03-09 22:11   ` Robert Richter
2020-03-10 11:41     ` Marc Zyngier
2020-03-10 12:34       ` Robert Richter
2020-03-11  8:45       ` Robert Richter
2020-03-11  9:03         ` Marc Zyngier
2020-03-11  9:18           ` Robert Richter
2019-12-24 11:10 ` [PATCH v3 04/32] irqchip/gic-v3: Use SGIs without active state if offered Marc Zyngier
2019-12-28  8:56   ` Zenghui Yu
2019-12-28 10:36     ` Marc Zyngier
2019-12-30  3:50       ` Zenghui Yu
2019-12-24 11:10 ` [PATCH v3 05/32] irqchip/gic-v4.1: VPE table (aka GICR_VPROPBASER) allocation Marc Zyngier
2020-01-20 14:03   ` Zenghui Yu
2020-01-20 15:11     ` Marc Zyngier
2020-01-22  2:59   ` Zenghui Yu
2019-12-24 11:10 ` [PATCH v3 06/32] irqchip/gic-v4.1: Implement the v4.1 flavour of VMAPP Marc Zyngier
2019-12-24 11:10 ` [PATCH v3 07/32] irqchip/gic-v4.1: Don't use the VPE proxy if RVPEID is set Marc Zyngier
2019-12-24 11:10 ` [PATCH v3 08/32] irqchip/gic-v4.1: Implement the v4.1 flavour of VMOVP Marc Zyngier
2019-12-24 11:10 ` [PATCH v3 09/32] irqchip/gic-v4.1: Plumb skeletal VPE irqchip Marc Zyngier
2019-12-24 11:10 ` [PATCH v3 10/32] irqchip/gic-v4.1: Add mask/unmask doorbell callbacks Marc Zyngier
2019-12-24 11:10 ` [PATCH v3 11/32] irqchip/gic-v4.1: Add VPE residency callback Marc Zyngier
2019-12-24 11:10 ` [PATCH v3 12/32] irqchip/gic-v4.1: Add VPE eviction callback Marc Zyngier
2019-12-24 11:10 ` [PATCH v3 13/32] irqchip/gic-v4.1: Add VPE INVALL callback Marc Zyngier
2019-12-24 11:10 ` [PATCH v3 14/32] irqchip/gic-v4.1: Suppress per-VLPI doorbell Marc Zyngier
2019-12-24 11:10 ` [PATCH v3 15/32] irqchip/gic-v4.1: Allow direct invalidation of VLPIs Marc Zyngier
2019-12-24 11:10 ` [PATCH v3 16/32] irqchip/gic-v4.1: Advertise support v4.1 to KVM Marc Zyngier
2019-12-24 11:10 ` [PATCH v3 17/32] irqchip/gic-v4.1: Map the ITS SGIR register page Marc Zyngier
2019-12-24 11:10 ` [PATCH v3 18/32] irqchip/gic-v4.1: Plumb skeletal VSGI irqchip Marc Zyngier
2019-12-24 11:10 ` [PATCH v3 19/32] irqchip/gic-v4.1: Add initial SGI configuration Marc Zyngier
2019-12-24 11:10 ` [PATCH v3 20/32] irqchip/gic-v4.1: Plumb mask/unmask SGI callbacks Marc Zyngier
2019-12-24 11:10 ` [PATCH v3 21/32] irqchip/gic-v4.1: Plumb get/set_irqchip_state " Marc Zyngier
2019-12-24 11:10 ` [PATCH v3 22/32] irqchip/gic-v4.1: Plumb set_vcpu_affinity " Marc Zyngier
2019-12-24 11:10 ` [PATCH v3 23/32] irqchip/gic-v4.1: Move doorbell management to the GICv4 abstraction layer Marc Zyngier
2019-12-24 11:10 ` [PATCH v3 24/32] irqchip/gic-v4.1: Add VSGI allocation/teardown Marc Zyngier
2019-12-24 11:10 ` [PATCH v3 25/32] irqchip/gic-v4.1: Add VSGI property setup Marc Zyngier
2019-12-24 11:10 ` [PATCH v3 26/32] irqchip/gic-v4.1: Eagerly vmap vPEs Marc Zyngier
2019-12-24 11:10 ` [PATCH v3 27/32] KVM: arm64: GICv4.1: Let doorbells be auto-enabled Marc Zyngier
2019-12-24 11:10 ` [PATCH v3 28/32] KVM: arm64: GICv4.1: Add direct injection capability to SGI registers Marc Zyngier
2019-12-28  9:19   ` Zenghui Yu
2019-12-28 10:41     ` Marc Zyngier
2019-12-24 11:10 ` [PATCH v3 29/32] KVM: arm64: GICv4.1: Allow SGIs to switch between HW and SW interrupts Marc Zyngier
2020-01-15  2:49   ` Shaokun Zhang
2020-01-15  3:49     ` Zenghui Yu
2020-01-15 13:32       ` Marc Zyngier
2020-01-15 13:49         ` Zenghui Yu
2020-01-16  6:13         ` Shaokun Zhang
2020-01-15 13:17     ` Marc Zyngier [this message]
2019-12-24 11:10 ` [PATCH v3 30/32] KVM: arm64: GICv4.1: Plumb SGI implementation selection in the distributor Marc Zyngier
2019-12-24 11:10 ` [PATCH v3 31/32] KVM: arm64: GICv4.1: Reload VLPI configuration on distributor enable/disable Marc Zyngier
2019-12-24 11:10 ` [PATCH v3 32/32] KVM: arm64: GICv4.1: Expose HW-based SGIs in debugfs Marc Zyngier

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