Re: [PATCH v5 10/26] KVM: arm/arm64: GICv4: Wire mapping/unmapping of VLPIs in VFIO irq bypass

[Marc Zyngier <marc.zyngier@arm.com>]

On 10/11/17 08:28, Christoffer Dall wrote:
> Hi Eric and Marc,
> 
> On Tue, Nov 07, 2017 at 02:42:44PM +0000, Marc Zyngier wrote:
>> Hi Eric,
>>
>> On 07/11/17 13:06, Auger Eric wrote:
>>> Hi Marc,
>>>
>>> On 27/10/2017 16:28, Marc Zyngier wrote:
>>>> Let's use the irq bypass mechanism introduced for platform device
>>>> interrupts
>>> nit: I would remove "introduced for platform device interrupts"
>>> as this is not upstream yet. x86 posted interrupts also use it.
>>>
>>>>
>>>  and establish our LPI->VLPI mapping.
> 
> I have tweaked the commit message.
> 
>>>>
>>>> Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
>>>> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
>>>> ---
>>>>  include/kvm/arm_vgic.h      |   8 ++++
>>>>  virt/kvm/arm/arm.c          |   6 ++-
>>>>  virt/kvm/arm/vgic/vgic-v4.c | 108 ++++++++++++++++++++++++++++++++++++++++++++
>>>>  3 files changed, 120 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
>>>> index 7eeb6c2a2f9c..2f750c770bf2 100644
>>>> --- a/include/kvm/arm_vgic.h
>>>> +++ b/include/kvm/arm_vgic.h
>>>> @@ -373,4 +373,12 @@ int kvm_vgic_setup_default_irq_routing(struct kvm *kvm);
>>>>  
>>>>  int kvm_vgic_set_owner(struct kvm_vcpu *vcpu, unsigned int intid, void *owner);
>>>>  
>>>> +struct kvm_kernel_irq_routing_entry;
>>>> +
>>>> +int kvm_vgic_v4_set_forwarding(struct kvm *kvm, int irq,
>>>> +			       struct kvm_kernel_irq_routing_entry *irq_entry);
>>>> +
>>>> +int kvm_vgic_v4_unset_forwarding(struct kvm *kvm, int irq,
>>>> +				 struct kvm_kernel_irq_routing_entry *irq_entry);
>>>> +
>>>>  #endif /* __KVM_ARM_VGIC_H */
>>>> diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
>>>> index 5d5218ecd547..8388c1cc23f6 100644
>>>> --- a/virt/kvm/arm/arm.c
>>>> +++ b/virt/kvm/arm/arm.c
>>>> @@ -1462,7 +1462,8 @@ int kvm_arch_irq_bypass_add_producer(struct irq_bypass_consumer *cons,
>>>>  	struct kvm_kernel_irqfd *irqfd =
>>>>  		container_of(cons, struct kvm_kernel_irqfd, consumer);
>>>>  
>>>> -	return 0;
>>>> +	return kvm_vgic_v4_set_forwarding(irqfd->kvm, prod->irq,
>>>> +					  &irqfd->irq_entry);
>>>>  }
>>>>  void kvm_arch_irq_bypass_del_producer(struct irq_bypass_consumer *cons,
>>>>  				      struct irq_bypass_producer *prod)
>>>> @@ -1470,7 +1471,8 @@ void kvm_arch_irq_bypass_del_producer(struct irq_bypass_consumer *cons,
>>>>  	struct kvm_kernel_irqfd *irqfd =
>>>>  		container_of(cons, struct kvm_kernel_irqfd, consumer);
>>>>  
>>>> -	return;
>>>> +	kvm_vgic_v4_unset_forwarding(irqfd->kvm, prod->irq,
>>>> +				     &irqfd->irq_entry);
>>>>  }
>>>>  
>>>>  void kvm_arch_irq_bypass_stop(struct irq_bypass_consumer *cons)
>>>> diff --git a/virt/kvm/arm/vgic/vgic-v4.c b/virt/kvm/arm/vgic/vgic-v4.c
>>>> index c794f0cef09e..01a2889b7b7c 100644
>>>> --- a/virt/kvm/arm/vgic/vgic-v4.c
>>>> +++ b/virt/kvm/arm/vgic/vgic-v4.c
>>>> @@ -18,6 +18,7 @@
>>>>  #include <linux/interrupt.h>
>>>>  #include <linux/irqdomain.h>
>>>>  #include <linux/kvm_host.h>
>>>> +#include <linux/irqchip/arm-gic-v3.h>
>>>>  
>>>>  #include "vgic.h"
>>>>  
>>>> @@ -81,3 +82,110 @@ void vgic_v4_teardown(struct kvm *kvm)
>>>>  	its_vm->nr_vpes = 0;
>>>>  	its_vm->vpes = NULL;
>>>>  }
>>>> +
>>>> +static struct vgic_its *vgic_get_its(struct kvm *kvm,
>>>> +				     struct kvm_kernel_irq_routing_entry *irq_entry)
>>>> +{
>>>> +	struct kvm_msi msi  = (struct kvm_msi) {
>>>> +		.address_lo	= irq_entry->msi.address_lo,
>>>> +		.address_hi	= irq_entry->msi.address_hi,
>>>> +		.data		= irq_entry->msi.data,
>>>> +		.flags		= irq_entry->msi.flags,
>>>> +		.devid		= irq_entry->msi.devid,
>>>> +	};
>>>> +
>>>> +	/*
>>>> +	 * Get a reference on the LPI. If NULL, this is not a valid
>>>> +	 * translation for any of our vITSs.
>>>> +	 */
>>> I don't understand the relevance of the above comment.
>>
>> Hmmm. The first part looks like an outdated leftover, as the ITS is not
>> refcounted, and we don't deal with LPIs here.
>>
> 
> I simply removed this comment.
> 
> [...]
> 
> I think the only thing left to fix on this patch is the IRQ_DISABLE_LAZY
> thing on its_map_vlpi() failures, which Marc can fix post -rc1.

Here's what I've queued on the irqchip side:

>From 9c0733704b99c89773416af3a412332b0e8bd2a4 Mon Sep 17 00:00:00 2001
From: Marc Zyngier <marc.zyngier@arm.com>
Date: Fri, 10 Nov 2017 09:00:41 +0000
Subject: [PATCH] irqchip/gic-v4: Clear IRQ_DISABLE_UNLAZY again if mapping
 fails

Should the call to irq_set_vcpu_affinity() fail at map time,
we should restore the normal lazy-disable behaviour instead
of staying with the eager disable that GICv4 requires.

Reported-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
 drivers/irqchip/irq-gic-v4.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/irqchip/irq-gic-v4.c b/drivers/irqchip/irq-gic-v4.c
index cd0bcc3b7e33..dba9d67cb9c1 100644
--- a/drivers/irqchip/irq-gic-v4.c
+++ b/drivers/irqchip/irq-gic-v4.c
@@ -177,6 +177,7 @@ int its_map_vlpi(int irq, struct its_vlpi_map *map)
 			.map      = map,
 		},
 	};
+	int ret;
 
 	/*
 	 * The host will never see that interrupt firing again, so it
@@ -184,7 +185,11 @@ int its_map_vlpi(int irq, struct its_vlpi_map *map)
 	 */
 	irq_set_status_flags(irq, IRQ_DISABLE_UNLAZY);
 
-	return irq_set_vcpu_affinity(irq, &info);
+	ret = irq_set_vcpu_affinity(irq, &info);
+	if (ret)
+		irq_clear_status_flags(irq, IRQ_DISABLE_UNLAZY);
+
+	return ret;
 }
 
 int its_get_vlpi(int irq, struct its_vlpi_map *map)
-- 
2.14.2


Thanks,

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