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Date: Wed, 09 Jan 2013 12:04:59 -0700
From: Alex Williamson <alex.williamson@...hat.com>
To: "Pandarathil, Vijaymohan R" <vijaymohan.pandarathil@...com>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>,
Gleb Natapov <gleb@...hat.com>,
"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
"qemu-devel@...gnu.org" <qemu-devel@...gnu.org>,
"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] VFIO-AER: Vfio-pci driver changes for supporting AER
On Wed, 2013-01-09 at 10:52 -0700, Alex Williamson wrote:
> On Wed, 2013-01-09 at 06:26 +0000, Pandarathil, Vijaymohan R wrote:
> > - New ioctl which is used to pass the eventfd that is signaled when
> > an error occurs in the vfio_pci_device
> >
> > - Register pci_error_handler for the vfio_pci driver
> >
> > - When the device encounters an error, the error handler registered by
> > the vfio_pci driver gets invoked by the AER infrastructure
> >
> > - In the error handler, signal the eventfd registered for the device.
> >
> > - This results in the qemu eventfd handler getting invoked and
> > appropriate action taken for the guest.
> >
> > Signed-off-by: Vijay Mohan Pandarathil <vijaymohan.pandarathil@...com>
> > ---
> > drivers/vfio/pci/vfio_pci.c | 29 +++++++++++++++++++++++++++++
> > drivers/vfio/pci/vfio_pci_private.h | 1 +
> > drivers/vfio/vfio.c | 8 ++++++++
> > include/linux/vfio.h | 1 +
> > include/uapi/linux/vfio.h | 9 +++++++++
> > 5 files changed, 48 insertions(+)
> >
> > diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
> > index 6c11994..4ae9526 100644
> > --- a/drivers/vfio/pci/vfio_pci.c
> > +++ b/drivers/vfio/pci/vfio_pci.c
> > @@ -207,6 +207,8 @@ static long vfio_pci_ioctl(void *device_data,
> > if (vdev->reset_works)
> > info.flags |= VFIO_DEVICE_FLAGS_RESET;
> >
> > + info.flags |= VFIO_DEVICE_FLAGS_AER_NOTIFY;
> > +
>
> This appears to be a PCI specific flag, so the name should include
> _PCI_. We also support non-PCIe devices and it seems like it would be
> possible to not have AER support available, so shouldn't this be
> conditional?
>
> > info.num_regions = VFIO_PCI_NUM_REGIONS;
> > info.num_irqs = VFIO_PCI_NUM_IRQS;
> >
> > @@ -348,6 +350,19 @@ static long vfio_pci_ioctl(void *device_data,
> >
> > return ret;
> >
> > + } else if (cmd == VFIO_DEVICE_SET_ERRFD) {
> > + int32_t fd = (int32_t)arg;
> > +
> > + if (fd < 0)
> > + return -EINVAL;
> > +
> > + vdev->err_trigger = eventfd_ctx_fdget(fd);
> > +
> > + if (IS_ERR(vdev->err_trigger))
> > + return PTR_ERR(vdev->err_trigger);
> > +
> > + return 0;
> > +
>
> I'm not sure why we wouldn't describe this as just another interrupt
> from the device and configure it via SET_IRQ. This ioctl has very
> limited use and doesn't follow any of the conventions of all the other
> vfio ioctls.
>
> > } else if (cmd == VFIO_DEVICE_RESET)
> > return vdev->reset_works ?
> > pci_reset_function(vdev->pdev) : -EINVAL;
> > @@ -527,11 +542,25 @@ static void vfio_pci_remove(struct pci_dev *pdev)
> > kfree(vdev);
> > }
> >
> > +static pci_ers_result_t vfio_err_detected(struct pci_dev *pdev,
> > + pci_channel_state_t state)
> > +{
> > + struct vfio_pci_device *vdev = vfio_get_vdev(&pdev->dev);
> > +
> > + eventfd_signal(vdev->err_trigger, 1);
> > + return PCI_ERS_RESULT_CAN_RECOVER;
> > +}
>
> What if err_trigger hasn't been set?
>
> > +
> > +static const struct pci_error_handlers vfio_err_handlers = {
> > + .error_detected = vfio_err_detected,
> > +};
> > +
> > static struct pci_driver vfio_pci_driver = {
> > .name = "vfio-pci",
> > .id_table = NULL, /* only dynamic ids */
> > .probe = vfio_pci_probe,
> > .remove = vfio_pci_remove,
> > + .err_handler = &vfio_err_handlers,
> > };
> >
> > static void __exit vfio_pci_cleanup(void)
> > diff --git a/drivers/vfio/pci/vfio_pci_private.h b/drivers/vfio/pci/vfio_pci_private.h
> > index 611827c..daee62f 100644
> > --- a/drivers/vfio/pci/vfio_pci_private.h
> > +++ b/drivers/vfio/pci/vfio_pci_private.h
> > @@ -55,6 +55,7 @@ struct vfio_pci_device {
> > bool bardirty;
> > struct pci_saved_state *pci_saved_state;
> > atomic_t refcnt;
> > + struct eventfd_ctx *err_trigger;
> > };
> >
> > #define is_intx(vdev) (vdev->irq_type == VFIO_PCI_INTX_IRQ_INDEX)
> > diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
> > index 56097c6..5ed5a54 100644
> > --- a/drivers/vfio/vfio.c
> > +++ b/drivers/vfio/vfio.c
> > @@ -693,6 +693,14 @@ void *vfio_del_group_dev(struct device *dev)
> > }
> > EXPORT_SYMBOL_GPL(vfio_del_group_dev);
> >
> > +void *vfio_get_vdev(struct device *dev)
> > +{
> > + struct vfio_device *device = dev_get_drvdata(dev);
> > +
> > + return device->device_data;
> > +}
> > +EXPORT_SYMBOL_GPL(vfio_get_vdev);
> > +
>
> This is unsafe. How do we know dev is a vfio device? How do we keep
> that drvdata valid while you're using it? I think you want to export
> the existing vfio_group_get_device() and vfio_device_put(). Thanks,
vfio_group_get_device() isn't quite what you want either since it
assumes a reference count on the group. You'll want something like
vfio_add_group_dev() or vfio_dev_present(), perhaps moving the
iommu_group_get -> vfio_group_get_from_iommu -> vfio_group_get_device
into a helper function. Thanks,
Alex
> > /**
> > * VFIO base fd, /dev/vfio/vfio
> > */
> > diff --git a/include/linux/vfio.h b/include/linux/vfio.h
> > index ab9e862..3c97b03 100644
> > --- a/include/linux/vfio.h
> > +++ b/include/linux/vfio.h
> > @@ -45,6 +45,7 @@ extern int vfio_add_group_dev(struct device *dev,
> > void *device_data);
> >
> > extern void *vfio_del_group_dev(struct device *dev);
> > +extern void *vfio_get_vdev(struct device *dev);
> >
> > /**
> > * struct vfio_iommu_driver_ops - VFIO IOMMU driver callbacks
> > diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> > index 4758d1b..fa67213 100644
> > --- a/include/uapi/linux/vfio.h
> > +++ b/include/uapi/linux/vfio.h
> > @@ -147,6 +147,7 @@ struct vfio_device_info {
> > __u32 flags;
> > #define VFIO_DEVICE_FLAGS_RESET (1 << 0) /* Device supports reset */
> > #define VFIO_DEVICE_FLAGS_PCI (1 << 1) /* vfio-pci device */
> > +#define VFIO_DEVICE_FLAGS_AER_NOTIFY (1 << 2) /* Supports aer notify */
> > __u32 num_regions; /* Max region index + 1 */
> > __u32 num_irqs; /* Max IRQ index + 1 */
> > };
> > @@ -288,6 +289,14 @@ struct vfio_irq_set {
> > */
> > #define VFIO_DEVICE_RESET _IO(VFIO_TYPE, VFIO_BASE + 11)
> >
> > +/**
> > + * VFIO_DEVICE_SET_ERRFD - _IO(VFIO_TYPE, VFIO_BASE + 12)
> > + *
> > + * Pass the eventfd to the vfio-pci driver for signalling any device
> > + * error notifications
> > + */
> > +#define VFIO_DEVICE_SET_ERRFD _IO(VFIO_TYPE, VFIO_BASE + 12)
> > +
> > /*
> > * The VFIO-PCI bus driver makes use of the following fixed region and
> > * IRQ index mapping. Unimplemented regions return a size of zero.
>
>
--
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