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Date: Thu, 20 Nov 2014 15:11:34 +0100
From: Antonios Motakis <a.motakis@...tualopensystems.com>
To: Eric Auger <eric.auger@...aro.org>
Cc: Alex Williamson <alex.williamson@...hat.com>,
kvm-arm <kvmarm@...ts.cs.columbia.edu>,
Linux IOMMU <iommu@...ts.linux-foundation.org>,
Will Deacon <will.deacon@....com>,
VirtualOpenSystems Technical Team <tech@...tualopensystems.com>,
Christoffer Dall <christoffer.dall@...aro.org>,
Kim Phillips <kim.phillips@...escale.com>,
Marc Zyngier <marc.zyngier@....com>,
"open list:VFIO DRIVER <kvm@...r.kernel.org>, open list"
<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v9 12/19] vfio/platform: trigger an interrupt via eventfd
On Wed, Nov 12, 2014 at 3:22 PM, Eric Auger <eric.auger@...aro.org> wrote:
> On 10/31/2014 08:36 PM, Alex Williamson wrote:
>> On Mon, 2014-10-27 at 19:07 +0100, Antonios Motakis wrote:
>>> This patch allows to set an eventfd for a patform device's interrupt,
> platform device (typo)
Ack.
>>> and also to trigger the interrupt eventfd from userspace for testing.
>>> Level sensitive interrupts are marked as maskable and are handled in
>>> a later patch. Edge triggered interrupts are not advertised as maskable
>>> and are implemented here using a simple and efficient IRQ handler.
>>>
>>> Signed-off-by: Antonios Motakis <a.motakis@...tualopensystems.com>
>>> ---
>>> drivers/vfio/platform/vfio_platform_irq.c | 93 ++++++++++++++++++++++++++-
>>> drivers/vfio/platform/vfio_platform_private.h | 2 +
>>> 2 files changed, 93 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/vfio/platform/vfio_platform_irq.c b/drivers/vfio/platform/vfio_platform_irq.c
>>> index 007b386..2ac8ed7 100644
>>> --- a/drivers/vfio/platform/vfio_platform_irq.c
>>> +++ b/drivers/vfio/platform/vfio_platform_irq.c
>>> @@ -45,11 +45,91 @@ static int vfio_platform_set_irq_unmask(struct vfio_platform_device *vdev,
>>> return -EINVAL;
>>> }
>>>
>>> +static irqreturn_t vfio_irq_handler(int irq, void *dev_id)
>>> +{
>>> + struct vfio_platform_irq *irq_ctx = dev_id;
>>> +
>>> + eventfd_signal(irq_ctx->trigger, 1);
>>> +
>>> + return IRQ_HANDLED;
>>> +}
>>> +
>>> +static int vfio_set_trigger(struct vfio_platform_device *vdev, int index,
>>> + int fd, irq_handler_t handler)
>>> +{
>>> + struct vfio_platform_irq *irq = &vdev->irqs[index];
>>> + struct eventfd_ctx *trigger;
>>> + int ret;
>>> +
>>> + if (irq->trigger) {
>>> + free_irq(irq->hwirq, irq);
>>> + kfree(irq->name);
>>> + eventfd_ctx_put(irq->trigger);
>>> + irq->trigger = NULL;
>>> + }
>>> +
>>> + if (fd < 0) /* Disable only */
>>> + return 0;
>>> +
>>> + irq->name = kasprintf(GFP_KERNEL, "vfio-irq[%d](%s)",
>>> + irq->hwirq, vdev->name);
>>> + if (!irq->name)
>>> + return -ENOMEM;
>>> +
>>> + trigger = eventfd_ctx_fdget(fd);
>>> + if (IS_ERR(trigger)) {
>>> + kfree(irq->name);
>>> + return PTR_ERR(trigger);
>>> + }
>>> +
>>> + irq->trigger = trigger;
>>> +
>>> + ret = request_irq(irq->hwirq, handler, 0, irq->name, irq);
>>> + if (ret) {
>>> + kfree(irq->name);
>>> + eventfd_ctx_put(trigger);
>>> + irq->trigger = NULL;
>>> + return ret;
>>> + }
>>> +
>>> + return 0;
> you may simply return ret here?
Indeed, ack.
>>> +}
>>> +
>>> static int vfio_platform_set_irq_trigger(struct vfio_platform_device *vdev,
>>> unsigned index, unsigned start,
>>> unsigned count, uint32_t flags, void *data)
>>> {
>>> - return -EINVAL;
>>> + struct vfio_platform_irq *irq = &vdev->irqs[index];
>>> + irq_handler_t handler;
>>> +
>>> + if (vdev->irqs[index].flags & VFIO_IRQ_INFO_MASKABLE)
>>> + return -EINVAL; /* not implemented */
>>> + else
>>> + handler = vfio_irq_handler;
>>> +
>>> + if (!count && (flags & VFIO_IRQ_SET_DATA_NONE))
>>> + return vfio_set_trigger(vdev, index, -1, handler);
>>> +
>>> + if (start != 0 || count != 1)
>>> + return -EINVAL;
>>> +
>>> + if (flags & VFIO_IRQ_SET_DATA_EVENTFD) {
>>> + int32_t fd = *(int32_t *)data;
>>> +
>>> + return vfio_set_trigger(vdev, index, fd, handler);
>>> + }
>>> +
>>> + if (flags & VFIO_IRQ_SET_DATA_NONE) {
>>> + handler(irq->hwirq, irq);
>>> +
>>> + } else if (flags & VFIO_IRQ_SET_DATA_BOOL) {
>>> + uint8_t trigger = *(uint8_t *)data;
>>> +
>>> + if (trigger)
>>> + handler(irq->hwirq, irq);
>>> + }
>>> +
>>> + return 0;
>>> }
>>>
>>> int vfio_platform_set_irqs_ioctl(struct vfio_platform_device *vdev,
>>> @@ -95,7 +175,11 @@ int vfio_platform_irq_init(struct vfio_platform_device *vdev)
>>> if (hwirq < 0)
>>> goto err;
>>>
>>> - vdev->irqs[i].flags = 0;
>>> + vdev->irqs[i].flags = VFIO_IRQ_INFO_EVENTFD;
>>> +
>>> + if (irq_get_trigger_type(hwirq) & IRQ_TYPE_LEVEL_MASK)
>>> + vdev->irqs[i].flags |= VFIO_IRQ_INFO_MASKABLE;
>>
>> This is a bit confusing because edge interrupts can support masking, but
>> they don't require it. Level interrupts really must support masking
>> because we need to mask them on the host and therefore the user needs to
>> be able to unmask them (ignoring the irq prioritization thing you guys
>> can do on arm). So this works, but I would really have expected
>> VFIO_IRQ_INFO_AUTOMASKED here and in the above function.
>
> Shouldn't we have AUTOMASKED for level sensitive and MASKABLE for both
> level & edge?
I believe it was Alex's argument to expose edge triggered irqs as
non-MASKABLE so they can benefit from a more efficient interrupt
handler.
Would it be acceptable to make them both maskable, but check for
masked status without a lock?
>
> For forwarded IRQ, may I enrich the external API with a new function
> enabling to turn the automasked flag off? Would that make sense?
Are you thinking of an external function but internal to the kernel,
or the external user API?
>
> Thanks
>
> Eric
>>
>>> +
>>> vdev->irqs[i].count = 1;
>>> vdev->irqs[i].hwirq = hwirq;
>>> }
>>> @@ -110,6 +194,11 @@ err:
>>>
>>> void vfio_platform_irq_cleanup(struct vfio_platform_device *vdev)
>>> {
>>> + int i;
>>> +
>>> + for (i = 0; i < vdev->num_irqs; i++)
>>> + vfio_set_trigger(vdev, i, -1, NULL);
>>> +
>>> vdev->num_irqs = 0;
>>> kfree(vdev->irqs);
>>> }
>>> diff --git a/drivers/vfio/platform/vfio_platform_private.h b/drivers/vfio/platform/vfio_platform_private.h
>>> index ffa2459..a3f2411 100644
>>> --- a/drivers/vfio/platform/vfio_platform_private.h
>>> +++ b/drivers/vfio/platform/vfio_platform_private.h
>>> @@ -28,6 +28,8 @@ struct vfio_platform_irq {
>>> u32 flags;
>>> u32 count;
>>> int hwirq;
>>> + char *name;
>>> + struct eventfd_ctx *trigger;
>>> };
>>>
>>> struct vfio_platform_region {
>>
>>
>>
>
--
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