Re: [Qemu-devel] [PATCH v4 3/3] QEMU-AER: Qemu changes to support AER for VFIO-PCI devices

[Alex Williamson]

On Thu, 2013-02-14 at 04:41 -0600, Vijay Mohan Pandarathil wrote:
>       - Create eventfd per vfio device assigned to a guest and register an
>           event handler
> 
>       - This fd is passed to the vfio_pci driver through the SET_IRQ ioctl
> 
>       - When the device encounters an error, the eventfd is signalled
>           and the qemu eventfd handler gets invoked.
> 
>       - In the handler decide what action to take. Current action taken
>           is to stop the guest.
> 
> Signed-off-by: Vijay Mohan Pandarathil <address@hidden>
> ---
>  hw/vfio_pci.c              | 112 
> +++++++++++++++++++++++++++++++++++++++++++++
>  linux-headers/linux/vfio.h |   1 +
>  2 files changed, 113 insertions(+)
> 
> diff --git a/hw/vfio_pci.c b/hw/vfio_pci.c
> index c51ae67..05da53b 100644
> --- a/hw/vfio_pci.c
> +++ b/hw/vfio_pci.c
> @@ -38,6 +38,7 @@
>  #include "qemu/error-report.h"
>  #include "qemu/queue.h"
>  #include "qemu/range.h"
> +#include "sysemu/sysemu.h"
>  
>  /* #define DEBUG_VFIO */
>  #ifdef DEBUG_VFIO
> @@ -129,7 +130,9 @@ typedef struct VFIODevice {
>      PCIHostDeviceAddress host;
>      QLIST_ENTRY(VFIODevice) next;
>      struct VFIOGroup *group;
> +    EventNotifier err_notifier;
>      bool reset_works;
> +    bool pci_aer;
>  } VFIODevice;
>  
>  typedef struct VFIOGroup {
> @@ -1802,6 +1805,7 @@ static int vfio_get_device(VFIOGroup *group, const char 
> *name, VFIODevice *vdev)
>  {
>      struct vfio_device_info dev_info = { .argsz = sizeof(dev_info) };
>      struct vfio_region_info reg_info = { .argsz = sizeof(reg_info) };
> +    struct vfio_irq_info irq_info = { .argsz = sizeof(irq_info) };
>      int ret, i;
>  
>      ret = ioctl(group->fd, VFIO_GROUP_GET_DEVICE_FD, name);
> @@ -1901,6 +1905,15 @@ static int vfio_get_device(VFIOGroup *group, const 
> char *name, VFIODevice *vdev)
>      vdev->config_size = reg_info.size;
>      vdev->config_offset = reg_info.offset;
>  
> +    irq_info.index = VFIO_PCI_ERR_IRQ_INDEX;
> +
> +    ret = ioctl(vdev->fd, VFIO_DEVICE_GET_IRQ_INFO, &irq_info);
> +    if (ret) {
> +        error_report("vfio: Error getting IRQ info: %m\n");

What if we're assigning a Legacy PCI device or running on an old kernel,
neither of these warrant an error_report.

> +        goto error;
> +    }
> +    if (irq_info.count == 1)
> +        vdev->pci_aer = true;

This is where I'd actually expect some kind of warning, you're getting
something back that you don't expect (if != 1).

>  error:
>      if (ret) {
>          QLIST_REMOVE(vdev, next);
> @@ -1922,6 +1935,102 @@ static void vfio_put_device(VFIODevice *vdev)
>      }
>  }
>  
> +static void vfio_err_notifier_handler(void *opaque)
> +{
> +    VFIODevice *vdev = opaque;
> +
> +    if (!event_notifier_test_and_clear(&vdev->err_notifier)) {
> +        return;
> +    }
> +
> +    /*
> +     * TBD. Retrieve the error details and decide what action
> +     * needs to be taken. One of the actions could be to pass
> +     * the error to the guest and have the guest driver recover
> +     * from the error. This requires that PCIe capabilities be
> +     * exposed to the guest. For now, we just terminate the
> +     * guest to contain the error.
> +     */
> +
> +    error_report("%s (%04x:%02x:%02x.%x)"
> +        "Unrecoverable error detected...\n"
> +        "Please inestigate/collect any data required and then kill the 
> quest",

s/inestigate/investigate/

This seems like a lot to ask of a user.

> +        __func__, vdev->host.domain, vdev->host.bus,
> +        vdev->host.slot, vdev->host.function);
> +
> +    vm_stop(RUN_STATE_IO_ERROR);

Gleb, were you looking for a new stop condition or is this one ok to
re-use?

> +}
> +
> +static void vfio_register_err_notifier(VFIODevice *vdev)
> +{
> +    int ret;
> +    int argsz;
> +    struct vfio_irq_set *irq_set;
> +    int32_t *pfd;
> +
> +    if (!vdev->pci_aer) {
> +        return;
> +    }
> +
> +    if (event_notifier_init(&vdev->err_notifier, 0)) {
> +        error_report("vfio: Warning: Unable to init event notifier for error 
> detection\n");
> +        return;
> +    }
> +
> +    argsz = sizeof(*irq_set) + sizeof(*pfd);
> +
> +    irq_set = g_malloc0(argsz);
> +    irq_set->argsz = argsz;
> +    irq_set->flags = VFIO_IRQ_SET_DATA_EVENTFD |
> +                     VFIO_IRQ_SET_ACTION_TRIGGER;
> +    irq_set->index = VFIO_PCI_ERR_IRQ_INDEX;
> +    irq_set->start = 0;
> +    irq_set->count = 1;
> +    pfd = (int32_t *)&irq_set->data;
> +
> +    *pfd = event_notifier_get_fd(&vdev->err_notifier);
> +    qemu_set_fd_handler(*pfd, vfio_err_notifier_handler, NULL, vdev);
> +
> +    ret = ioctl(vdev->fd, VFIO_DEVICE_SET_IRQS, irq_set);
> +    if (ret) {
> +        error_report("vfio: Failed to set up error notification\n");
> +        qemu_set_fd_handler(*pfd, NULL, NULL, vdev);
> +        event_notifier_cleanup(&vdev->err_notifier);
> +    }
> +    g_free(irq_set);
> +}

Why does the register return void?  If it's supported and fails, isn't
that a condition where we'd want to fail the initfn?  Also, if the above
fails, there's nothing that prevents the below unreqister... isn't that
a bug?

> +static void vfio_unregister_err_notifier(VFIODevice *vdev)
> +{
> +    int argsz;
> +    struct vfio_irq_set *irq_set;
> +    int32_t *pfd;
> +    int ret;
> +
> +    if (!vdev->pci_aer) {
> +        return;
> +    }
> +
> +    argsz = sizeof(*irq_set) + sizeof(*pfd);
> +
> +    irq_set = g_malloc0(argsz);
> +    irq_set->argsz = argsz;
> +    irq_set->flags = VFIO_IRQ_SET_DATA_EVENTFD |
> +                     VFIO_IRQ_SET_ACTION_TRIGGER;
> +    irq_set->index = VFIO_PCI_ERR_IRQ_INDEX;
> +    irq_set->start = 0;
> +    irq_set->count = 1;
> +    pfd = (int32_t *)&irq_set->data;
> +    *pfd = -1;
> +
> +    ret = ioctl(vdev->fd, VFIO_DEVICE_SET_IRQS, irq_set);
> +    if (ret) {
> +        error_report("vfio: Failed to de-assign error fd: %d\n", ret);
> +    }
> +    g_free(irq_set);
> +    qemu_set_fd_handler(event_notifier_get_fd(&vdev->err_notifier),
> +                        NULL, NULL, vdev);
> +    event_notifier_cleanup(&vdev->err_notifier);
> +}
>  static int vfio_initfn(PCIDevice *pdev)
>  {
>      VFIODevice *pvdev, *vdev = DO_UPCAST(VFIODevice, pdev, pdev);
> @@ -2032,6 +2141,8 @@ static int vfio_initfn(PCIDevice *pdev)
>          }
>      }
>  
> +    vfio_register_err_notifier(vdev);
> +
>      return 0;
>  
>  out_teardown:
> @@ -2049,6 +2160,7 @@ static void vfio_exitfn(PCIDevice *pdev)
>      VFIODevice *vdev = DO_UPCAST(VFIODevice, pdev, pdev);
>      VFIOGroup *group = vdev->group;
>  
> +    vfio_unregister_err_notifier(vdev);
>      pci_device_set_intx_routing_notifier(&vdev->pdev, NULL);
>      vfio_disable_interrupts(vdev);
>      if (vdev->intx.mmap_timer) {
> diff --git a/linux-headers/linux/vfio.h b/linux-headers/linux/vfio.h
> index f787b72..6b20849 100644
> --- a/linux-headers/linux/vfio.h
> +++ b/linux-headers/linux/vfio.h
> @@ -310,6 +310,7 @@ enum {
>       VFIO_PCI_INTX_IRQ_INDEX,
>       VFIO_PCI_MSI_IRQ_INDEX,
>       VFIO_PCI_MSIX_IRQ_INDEX,
> +     VFIO_PCI_ERR_IRQ_INDEX,
>       VFIO_PCI_NUM_IRQS
>  };
>  

Linux headers get updated via the scripts/update-linux-headers.sh
script.  This will need to be done in a separate patch after the kernel
changes are upstream.  Thanks,

Alex