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

Marc Zyngier
2017-11-10T09:03:29Z

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...