Re: [Qemu-devel] [PATCH v9 10/11] vfio: Add waiting for host aer error progress

[Cao jin]

Hi

On 07/19/2016 03:38 PM, Zhou Jie wrote:
> From: Chen Fan <address@hidden>
>
> For supporting aer recovery, host and guest would run the same aer
> recovery code, that would do the secondary bus reset if the error
> is fatal, the aer recovery process:
>    1. error_detected
>    2. reset_link (if fatal)
>    3. slot_reset/mmio_enabled
>    4. resume
>
> It indicates that host will do secondary bus reset to reset
> the physical devices under bus in step 2, that would cause
> devices in D3 status in a short time. But in qemu, we register
> an error detected handler, that would be invoked as host broadcasts
> the error-detected event in step 1, in order to avoid guest do
> reset_link when host do reset_link simultaneously. it may cause
> fatal error. we poll the vfio_device_info to assure host reset
> completely.
> In qemu, the aer recovery process:
>    1. Detect support for aer error progress
>       If host vfio driver does not support for aer error progress,
>       directly fail to boot up VM as with aer enabled.
>    2. Immediately notify the VM on error detected.
>    3. Wait for host aer error progress
>       Poll the vfio_device_info, If it is still in aer error progress after
>       some timeout, we would abort the guest directed bus reset
>       altogether and unplug of the device to prevent it from further
>       interacting with the VM.
>    4. Reset bus.

I have question about step 4(Reset bus). When guest reset link, guest 
set 'secondary bus reset' bit, then devices under the bus would do reset 
themselves separately. For vfio-pci, the emulated device, I think the 
previous logic[*] is fine. But now process looks like following:

1. One affected device: we do(or wait & do) bus 
reset(vfio_pci_hot_reset) directly
2. N affected devices: function 0 will do the same as 1.
   other affected devices will do nothing, just return.

these logic seems weird to me, are these what we want?

I don't see why we don't use the previous 'reset priority' for each 
vfio-pci emulated devices.

[*]reset priority
     1. If has "device specific reset function", then do it
     2. If has FLR, then do it.
     3. If it can do bus reset(only 1 affected device), then do it
     4. If has pm_reset, then do it

This is what I think:

static void vfio_pci_reset(DeviceState *dev)
{
    PCIDevice *pdev = DO_UPCAST(PCIDevice, qdev, dev);
    VFIOPCIDevice *vdev = DO_UPCAST(VFIOPCIDevice, pdev, pdev);
    int i;

    for (i = 0; i < 1000; i++) {
        if (!vfio_aer_error_is_in_process(vdev)) {
            break;
        }
        g_usleep(PCI_AER_PROCESS_TIMEOUT / 1000);
    }

    if (i == 1000) {
        qdev_unplug(&vdev->pdev.qdev, NULL);
    } else {
        trace_vfio_pci_reset(vdev->vbasedev.name);

        vfio_pci_pre_reset(vdev);

        if (vdev->resetfn && !vdev->resetfn(vdev)) {
            goto post_reset;
        }

        if (vdev->vbasedev.reset_works &&
            (vdev->has_flr || !vdev->has_pm_reset) &&
            !ioctl(vdev->vbasedev.fd, VFIO_DEVICE_RESET)) {
            trace_vfio_pci_reset_flr(vdev->vbasedev.name);
            goto post_reset;
        }

        /* See if we can do our own bus reset */
        if (!vfio_pci_hot_reset_one(vdev)) {
            goto post_reset;
        }

        /* If nothing else works and the device supports PM reset, use 
it */
        if (vdev->vbasedev.reset_works && vdev->has_pm_reset &&
            !ioctl(vdev->vbasedev.fd, VFIO_DEVICE_RESET)) {
            trace_vfio_pci_reset_pm(vdev->vbasedev.name);
            goto post_reset;
        }
    }

post_reset:
    vfio_pci_post_reset(vdev);
}

Cao jin

> Signed-off-by: Chen Fan <address@hidden>
> Signed-off-by: Zhou Jie <address@hidden>
> ---
>   hw/vfio/pci.c              | 51 +++++++++++++++++++++++++++++++++++++++++++++-
>   hw/vfio/pci.h              |  1 +
>   linux-headers/linux/vfio.h |  4 ++++
>   3 files changed, 55 insertions(+), 1 deletion(-)
>
> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
> index 0e42786..777245c 100644
> --- a/hw/vfio/pci.c
> +++ b/hw/vfio/pci.c
> @@ -35,6 +35,12 @@
>
>   #define MSIX_CAP_LENGTH 12
>
> +/*
> + * Timeout for waiting host aer error process, it is 3 seconds.
> + * For hardware bus reset 3 seconds will be enough.
> + */
> +#define PCI_AER_PROCESS_TIMEOUT 3000000
> +
>   static void vfio_disable_interrupts(VFIOPCIDevice *vdev);
>   static void vfio_mmap_set_enabled(VFIOPCIDevice *vdev, bool enabled);
>
> @@ -1913,6 +1919,14 @@ static void vfio_check_hot_bus_reset(VFIOPCIDevice 
> *vdev, Error **errp)
>       VFIOGroup *group;
>       int ret, i, devfn, range_limit;
>
> +    if (!(vdev->vbasedev.flags & VFIO_DEVICE_FLAGS_AERPROCESS)) {
> +        error_setg(errp, "vfio: Cannot enable AER for device %s,"
> +                   " host vfio driver does not support for"
> +                   " aer error progress",
> +                   vdev->vbasedev.name);
> +        return;
> +    }
> +
>       ret = vfio_get_hot_reset_info(vdev, &info);
>       if (ret) {
>           error_setg(errp, "vfio: Cannot enable AER for device %s,"
> @@ -2679,6 +2693,11 @@ static void vfio_err_notifier_handler(void *opaque)
>           msg.severity = isfatal ? PCI_ERR_ROOT_CMD_FATAL_EN :
>                                    PCI_ERR_ROOT_CMD_NONFATAL_EN;
>
> +        if (isfatal) {
> +            PCIDevice *dev_0 = pci_get_function_0(dev);
> +            VFIOPCIDevice *vdev_0 = DO_UPCAST(VFIOPCIDevice, pdev, dev_0);
> +            vdev_0->pci_aer_error_signaled = true;
> +        }
>           pcie_aer_msg(dev, &msg);
>           return;
>       }
> @@ -3163,6 +3182,19 @@ static void vfio_exitfn(PCIDevice *pdev)
>       vfio_bars_exit(vdev);
>   }
>
> +static int vfio_aer_error_is_in_process(VFIOPCIDevice *vdev)
> +{
> +    struct vfio_device_info dev_info = { .argsz = sizeof(dev_info) };
> +    int ret;
> +
> +    ret = ioctl(vdev->vbasedev.fd, VFIO_DEVICE_GET_INFO, &dev_info);
> +    if (ret) {
> +        error_report("vfio: error getting device info: %m");
> +        return ret;
> +    }
> +    return dev_info.flags & VFIO_DEVICE_FLAGS_INAERPROCESS ? 1 : 0;
> +}
> +
>   static void vfio_pci_reset(DeviceState *dev)
>   {
>       PCIDevice *pdev = DO_UPCAST(PCIDevice, qdev, dev);
> @@ -3176,7 +3208,24 @@ static void vfio_pci_reset(DeviceState *dev)
>           if ((pci_get_word(br->config + PCI_BRIDGE_CONTROL) &
>                PCI_BRIDGE_CTL_BUS_RESET)) {
>               if (pci_get_function_0(pdev) == pdev) {
> -                vfio_pci_hot_reset(vdev, vdev->single_depend_dev);
> +                if (!vdev->pci_aer_error_signaled) {
> +                    vfio_pci_hot_reset(vdev, vdev->single_depend_dev);
> +                } else {
> +                    int i;
> +                    for (i = 0; i < 1000; i++) {
> +                        if (!vfio_aer_error_is_in_process(vdev)) {
> +                            break;
> +                        }
> +                        g_usleep(PCI_AER_PROCESS_TIMEOUT / 1000);
> +                    }
> +
> +                    if (i == 1000) {
> +                        qdev_unplug(&vdev->pdev.qdev, NULL);
> +                    } else {
> +                        vfio_pci_hot_reset(vdev, vdev->single_depend_dev);
> +                    }
> +                    vdev->pci_aer_error_signaled = false;
> +                }
>               }
>               return;
>           }
> diff --git a/hw/vfio/pci.h b/hw/vfio/pci.h
> index ed14322..c9e0202 100644
> --- a/hw/vfio/pci.h
> +++ b/hw/vfio/pci.h
> @@ -148,6 +148,7 @@ typedef struct VFIOPCIDevice {
>       bool no_kvm_msi;
>       bool no_kvm_msix;
>       bool single_depend_dev;
> +    bool pci_aer_error_signaled;
>   } VFIOPCIDevice;
>
>   uint32_t vfio_pci_read_config(PCIDevice *pdev, uint32_t addr, int len);
> diff --git a/linux-headers/linux/vfio.h b/linux-headers/linux/vfio.h
> index 759b850..9295fca 100644
> --- a/linux-headers/linux/vfio.h
> +++ b/linux-headers/linux/vfio.h
> @@ -198,6 +198,10 @@ struct vfio_device_info {
>   #define VFIO_DEVICE_FLAGS_PCI (1 << 1)  /* vfio-pci device */
>   #define VFIO_DEVICE_FLAGS_PLATFORM (1 << 2)     /* vfio-platform device */
>   #define VFIO_DEVICE_FLAGS_AMBA  (1 << 3)        /* vfio-amba device */
> +/* support aer error progress */
> +#define VFIO_DEVICE_FLAGS_AERPROCESS  (1 << 4)
> +/* status in aer error progress */
> +#define VFIO_DEVICE_FLAGS_INAERPROCESS  (1 << 5)
>         __u32   num_regions;    /* Max region index + 1 */
>         __u32   num_irqs;       /* Max IRQ index + 1 */
>   };