Re: [Qemu-devel] [RFC v8.1 12/13] vfio-pci: pass the aer error to guest

[Alex Williamson <alex.williamson@redhat.com>]

On Wed, 2015-05-27 at 10:46 +0800, Chen Fan wrote:
> when the vfio device encounters an uncorrectable error in host,
> the vfio_pci driver will signal the eventfd registered by this
> vfio device, the results in the qemu eventfd handler getting
> invoked.
> 
> this patch is to pass the error to guest and have the guest driver
> recover from the error.
> 
> Signed-off-by: Chen Fan <chen.fan.fnst@cn.fujitsu.com>
> ---
>  hw/vfio/pci.c | 42 ++++++++++++++++++++++++++++++++++++------
>  1 file changed, 36 insertions(+), 6 deletions(-)
> 
> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
> index b05ccdf..855a0a6 100644
> --- a/hw/vfio/pci.c
> +++ b/hw/vfio/pci.c
> @@ -3348,18 +3348,48 @@ static void vfio_put_device(VFIOPCIDevice *vdev)
>  static void vfio_err_notifier_handler(void *opaque)
>  {
>      VFIOPCIDevice *vdev = opaque;
> +    PCIDevice *dev = &vdev->pdev;
> +    PCIEAERMsg msg = {
> +        .severity = 0,
> +        .source_id = (pci_bus_num(dev->bus) << 8) | dev->devfn,
> +    };
>  
>      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.
> +     * in case the real hardware configration has been changed,
> +     * here we should recheck the bus reset capability.
> +     */
> +    vfio_check_host_bus_reset(vdev);

Why would we run this on devices without the AER feature?  I agree that
we do need to revalidate for devices that are exposing AER forwarding.

> +
> +    /*
> +     * we should read the error details from the real hardware
> +     * configuration spaces, here we only need to do is signaling
> +     * to guest an uncorrectable error has occurred.
> +     */
> +    if (dev->exp.aer_cap &&
> +        vdev->has_bus_reset) {
> +        uint8_t *aer_cap = dev->config + dev->exp.aer_cap;
> +        uint32_t uncor_status;
> +        bool isfatal;
> +
> +        uncor_status = vfio_pci_read_config(dev,
> +                           dev->exp.aer_cap + PCI_ERR_UNCOR_STATUS, 4);
> +
> +        isfatal = uncor_status & pci_get_long(aer_cap + PCI_ERR_UNCOR_SEVER);
> +
> +        msg.severity = isfatal ? PCI_ERR_ROOT_CMD_FATAL_EN :
> +                                 PCI_ERR_ROOT_CMD_NONFATAL_EN;
> +
> +        pcie_aer_msg(dev, &msg);
> +        return;
> +    }
> +
> +    /*
> +     * If the aer capability is not exposed to the guest. we just
> +     * terminate the guest to contain the error.
>       */
>  
>      error_report("%s(%04x:%02x:%02x.%x) Unrecoverable error detected.  "