Re: [RFC PATCH v6 15/20] vfio/platform: support for maskable and automasked interrupts

Antonios Motakis
2014-09-02T16:06:40Z

On Sun, Jun 8, 2014 at 12:17 PM, Christoffer Dall
<christoffer.dall@linaro.org> wrote:
> On Thu, Jun 05, 2014 at 07:03:23PM +0200, Antonios Motakis wrote:
>> Adds support to mask interrupts, and also for automasked interrupts.
>> Level sensitive interrupts are exposed as automasked interrupts and
>> are masked and disabled automatically when they fire.
>>
>> Signed-off-by: Antonios Motakis <a.motakis@virtualopensystems.com>
>> ---
>> drivers/vfio/platform/vfio_platform_irq.c | 112 ++++++++++++++++++++++++--
>> drivers/vfio/platform/vfio_platform_private.h | 2 +
>> 2 files changed, 109 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/vfio/platform/vfio_platform_irq.c b/drivers/vfio/platform/vfio_platform_irq.c
>> index d79f5af..10dfbf0 100644
>> --- a/drivers/vfio/platform/vfio_platform_irq.c
>> +++ b/drivers/vfio/platform/vfio_platform_irq.c
>> @@ -51,9 +51,17 @@ int vfio_platform_irq_init(struct vfio_platform_device *vdev)
>> if (hwirq < 0)
>> goto err;
>>
>> - vdev->irq[i].flags = VFIO_IRQ_INFO_EVENTFD;
>> + spin_lock_init(&vdev->irq[i].lock);
>> +
>> + vdev->irq[i].flags = VFIO_IRQ_INFO_EVENTFD
>> + | VFIO_IRQ_INFO_MASKABLE;
>> +
>> + if (irq_get_trigger_type(hwirq) & IRQ_TYPE_LEVEL_MASK)
>> + vdev->irq[i].flags |= VFIO_IRQ_INFO_AUTOMASKED;
>
> This seems to rely on the fact that you had actually loaded a driver for
> your device to set the right type. Is this assumption always correct?
>
> It seems to me that this configuration bit should now be up to your user
> space drive who is the best candidate to know details about your device
> at this point?
>

Hm, I see this type being set usually either in a device tree source,
or in the support code for a specific platform. Are there any
situations where this is actually set by the driver? If I understand
right this is not the case for the PL330, but if it is possible that
it is the case for another device then I need to rethink this. Though
as far as I understand this should not be the case.

>> +
>> vdev->irq[i].count = 1;
>> vdev->irq[i].hwirq = hwirq;
>> + vdev->irq[i].masked = false;
>> }
>>
>> vdev->num_irqs = cnt;
>> @@ -77,11 +85,27 @@ void vfio_platform_irq_cleanup(struct vfio_platform_device *vdev)
>>
>> static irqreturn_t vfio_irq_handler(int irq, void *dev_id)
>> {
>> - struct eventfd_ctx *trigger = dev_id;
>> + struct vfio_platform_irq *irq_ctx = dev_id;
>> + unsigned long flags;
>> + int ret = IRQ_NONE;
>> +
>> + spin_lock_irqsave(&irq_ctx->lock, flags);
>> +
>> + if (!irq_ctx->masked) {
>> + ret = IRQ_HANDLED;
>> +
>> + if (irq_ctx->flags & VFIO_IRQ_INFO_AUTOMASKED) {
>> + disable_irq_nosync(irq_ctx->hwirq);
>> + irq_ctx->masked = true;
>> + }
>> + }
>>
>> - eventfd_signal(trigger, 1);
>> + spin_unlock_irqrestore(&irq_ctx->lock, flags);
>>
>> - return IRQ_HANDLED;
>> + if (ret == IRQ_HANDLED)
>> + eventfd_signal(irq_ctx->trigger, 1);
>> +
>> + return ret;
>> }
>>
>> static int vfio_set_trigger(struct vfio_platform_device *vdev,
>> @@ -162,6 +186,82 @@ static int vfio_platform_set_irq_trigger(struct vfio_platform_device *vdev,
>> return -EFAULT;
>> }
>>
>> +static int vfio_platform_set_irq_unmask(struct vfio_platform_device *vdev,
>> + unsigned index, unsigned start,
>> + unsigned count, uint32_t flags, void *data)
>> +{
>> + uint8_t arr;
>
>
> arr?

arr for array! As in, the VFIO API allows an array of IRQs. However
for platform devices we don't use this, each IRQ is exposed
independently as an array of 1 IRQ.

>
>> +
>> + if (start != 0 || count != 1)
>> + return -EINVAL;
>> +
>> + switch (flags & VFIO_IRQ_SET_DATA_TYPE_MASK) {
>> + case VFIO_IRQ_SET_DATA_BOOL:
>> + if (copy_from_user(&arr, data, sizeof(uint8_t)))
>> + return -EFAULT;
>> +
>> + if (arr != 0x1)
>> + return -EINVAL;
>
> why the fallthrough, what's this about?

The VFIO API allows to unmask/mask an array of IRQs, however with
platform devices we only have arrays of 1 IRQ (so not really arrays).

So if the user uses VFIO_IRQ_SET_DATA_BOOL, we need to check that arr
== 0x1. When that is the case, a fallthrough to the same code for
VFIO_IRQ_SET_DATA_NONE is safe.

If that is not readable enough, then I can add a comment or duplicate
the code that does the unmasking. I realize that if you don't know the
VFIO API well, then this can look confusing.

>
>> +
>> + case VFIO_IRQ_SET_DATA_NONE:
>> +
>> + spin_lock_irq(&vdev->irq[index].lock);
>> +
>> + if (vdev->irq[index].masked) {
>> + enable_irq(vdev->irq[index].hwirq);
>> + vdev->irq[index].masked = false;
>> + }
>> +
>> + spin_unlock_irq(&vdev->irq[index].lock);
>> +
>> + return 0;
>> +
>> + case VFIO_IRQ_SET_DATA_EVENTFD: /* XXX not implemented yet */
>> + default:
>> + return -ENOTTY;
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +static int vfio_platform_set_irq_mask(struct vfio_platform_device *vdev,
>> + unsigned index, unsigned start,
>> + unsigned count, uint32_t flags, void *data)
>> +{
>> + uint8_t arr;
>> +
>> + if (start != 0 || count != 1)
>> + return -EINVAL;
>> +
>> + switch (flags & VFIO_IRQ_SET_DATA_TYPE_MASK) {
>> + case VFIO_IRQ_SET_DATA_BOOL:
>> + if (copy_from_user(&arr, data, sizeof(uint8_t)))
>> + return -EFAULT;
>> +
>> + if (arr != 0x1)
>> + return -EINVAL;
>> +
>> + case VFIO_IRQ_SET_DATA_NONE:
>> +
>> + spin_lock_irq(&vdev->irq[index].lock);
>> +
>> + if (!vdev->irq[index].masked) {
>> + disable_irq(vdev->irq[index].hwirq);
>> + vdev->irq[index].masked = true;
>> + }
>> +
>> + spin_unlock_irq(&vdev->irq[index].lock);
>> +
>> + return 0;
>> +
>> + case VFIO_IRQ_SET_DATA_EVENTFD: /* XXX not implemented yet */
>> + default:
>> + return -ENOTTY;
>> + }
>> +
>> + return 0;
>> +}
>> +
>> int vfio_platform_set_irqs_ioctl(struct vfio_platform_device *vdev,
>> uint32_t flags, unsigned index, unsigned start,
>> unsigned count, void *data)
>> @@ -172,8 +272,10 @@ int vfio_platform_set_irqs_ioctl(struct vfio_platform_device *vdev,
>>
>> switch (flags & VFIO_IRQ_SET_ACTION_TYPE_MASK) {
>> case VFIO_IRQ_SET_ACTION_MASK:
>> + func = vfio_platform_set_irq_mask;
>> + break;
>> case VFIO_IRQ_SET_ACTION_UNMASK:
>> - /* XXX not implemented */
>> + func = vfio_platform_set_irq_unmask;
>> break;
>> case VFIO_IRQ_SET_ACTION_TRIGGER:
>> func = vfio_platform_set_irq_trigger;
>> diff --git a/drivers/vfio/platform/vfio_platform_private.h b/drivers/vfio/platform/vfio_platform_private.h
>> index d6200df..4d887fd 100644
>> --- a/drivers/vfio/platform/vfio_platform_private.h
>> +++ b/drivers/vfio/platform/vfio_platform_private.h
>> @@ -30,6 +30,8 @@ struct vfio_platform_irq {
>> u32 count;
>> int hwirq;
>> char *name;
>> + bool masked;
>> + spinlock_t lock;
>> };
>>
>> struct vfio_platform_region {
>> --
>> 1.8.3.2
>>

--
Antonios Motakis
Virtual Open Systems