Re: [PATCH] vfio pci: kernel support of error recovery only for non fatal error

[Michael S. Tsirkin]

On Mon, Feb 27, 2017 at 03:28:43PM +0800, Cao jin wrote:
> Subject: Re: [PATCH] vfio pci: kernel support of error recovery only for non
> fatal error

Don't make the subject so long. This is why I had
	[PATCH v3] vfio error recovery: kernel support
you also want to add versioning as you inherited my v3,
you should make this v4 etc.

> 0. What happens now (PCIE AER only)
>    Fatal errors cause a link reset.
>    Non fatal errors don't.
>    All errors stop the VM eventually, but not immediately
>    because it's detected and reported asynchronously.
>    Interrupts are forwarded as usual.
>    Correctable errors are not reported to guest at all.
>    Note: PPC EEH is different. This focuses on AER.
> 
> 1. Correctable errors
>    There is no need to report these to guest. So let's not.
> 
> 2. Fatal errors
>    It's not easy to handle them gracefully since link reset
>    is needed. As a first step, let's use the existing mechanism
>    in that case.
> 
> 2. Non-fatal errors
>    Here we could make progress by reporting them to guest
>    and have guest handle them.
> 
>    Issues:
>    a. this behaviour should only be enabled with new userspace,
>       old userspace should work without changes.
> 
>       Suggestion: One way to address this would be to add a new eventfd
>       non_fatal_err_trigger. If not set, invoke err_trigger.
> 
>    b. drivers are supposed to stop MMIO when error is reported,
>       if vm keeps going, we will keep doing MMIO/config.
> 
>       Suggestion 1: ignore this. vm stop happens much later when
>       userspace runs anyway, so we are not making things much worse.
> 
>       Suggestion 2: try to stop MMIO/config, resume on resume call
> 
>       Patch below implements Suggestion 1.
> 
>       Note that although this is really against the documentation, which
>       states error_detected() is the point at which the driver should quiesce
>       the device and not touch it further (until diagnostic poking at
>       mmio_enabled or full access at resume callback).
> 
>       Fixing this won't be easy. However, this is not a regression.
> 
>       Also note this does nothing about interrupts, documentation
>       suggests returning IRQ_NONE until reset.
>       Again, not a regression.
> 
>    c. PF driver might detect that function is completely broken,
>       if vm keeps going, we will keep doing MMIO/config.
> 
>       Suggestion 1: ignore this. vm stop happens much later when
>       userspace runs anyway, so we are not making things much worse.
> 
>       Suggestion 2: detect this and invoke err_trigger to stop VM.
> 
>       Patch below implements Suggestion 2.
> 
> Suggested-by: Michael S. Tsirkin <mst@xxxxxxxxxx>

It's more than this, you are really reusing parts of my patch,
so you should say so and include my signature.

If you only added a line or two you can keep
the original author. To do this you add
	From: Michael S. Tsirkin <mst@xxxxxxxxxx>
before commit text.

> Signed-off-by: Cao jin <caoj.fnst@xxxxxxxxxxxxxx>
> ---

Changelog from my v3?

>  drivers/vfio/pci/vfio_pci.c         | 38 +++++++++++++++++++++++++++++++++++--
>  drivers/vfio/pci/vfio_pci_intrs.c   | 19 +++++++++++++++++++
>  drivers/vfio/pci/vfio_pci_private.h |  1 +
>  include/uapi/linux/vfio.h           |  1 +
>  4 files changed, 57 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
> index 324c52e..3551cc9 100644
> --- a/drivers/vfio/pci/vfio_pci.c
> +++ b/drivers/vfio/pci/vfio_pci.c
> @@ -441,7 +441,8 @@ static int vfio_pci_get_irq_count(struct vfio_pci_device *vdev, int irq_type)
>  
>  			return (flags & PCI_MSIX_FLAGS_QSIZE) + 1;
>  		}
> -	} else if (irq_type == VFIO_PCI_ERR_IRQ_INDEX) {
> +	} else if (irq_type == VFIO_PCI_ERR_IRQ_INDEX ||
> +		   irq_type == VFIO_PCI_NON_FATAL_ERR_IRQ_INDEX) {
>  		if (pci_is_pcie(vdev->pdev))
>  			return 1;
>  	} else if (irq_type == VFIO_PCI_REQ_IRQ_INDEX) {
> @@ -796,6 +797,7 @@ static long vfio_pci_ioctl(void *device_data,
>  		case VFIO_PCI_REQ_IRQ_INDEX:
>  			break;
>  		case VFIO_PCI_ERR_IRQ_INDEX:
> +		case VFIO_PCI_NON_FATAL_ERR_IRQ_INDEX:
>  			if (pci_is_pcie(vdev->pdev))
>  				break;
>  		/* pass thru to return error */
> @@ -1282,7 +1284,9 @@ static pci_ers_result_t vfio_pci_aer_err_detected(struct pci_dev *pdev,
>  
>  	mutex_lock(&vdev->igate);
>  
> -	if (vdev->err_trigger)
> +	if (state == pci_channel_io_normal && vdev->non_fatal_err_trigger)
> +		eventfd_signal(vdev->non_fatal_err_trigger, 1);
> +	else if (vdev->err_trigger)
>  		eventfd_signal(vdev->err_trigger, 1);
>  
>  	mutex_unlock(&vdev->igate);
> @@ -1292,8 +1296,38 @@ static pci_ers_result_t vfio_pci_aer_err_detected(struct pci_dev *pdev,
>  	return PCI_ERS_RESULT_CAN_RECOVER;
>  }
>  
> +static pci_ers_result_t vfio_pci_aer_slot_reset(struct pci_dev *pdev)
> +{
> +	struct vfio_pci_device *vdev;
> +	struct vfio_device *device;
> +	static pci_ers_result_t err = PCI_ERS_RESULT_NONE;
> +
> +	device = vfio_device_get_from_dev(&pdev->dev);
> +	if (!device)
> +		goto err_dev;
> +
> +	vdev = vfio_device_data(device);
> +	if (!vdev)
> +		goto err_data;
> +
> +	mutex_lock(&vdev->igate);
> +
> +	if (vdev->err_trigger)
> +		eventfd_signal(vdev->err_trigger, 1);
> +
> +	mutex_unlock(&vdev->igate);
> +
> +	err = PCI_ERS_RESULT_RECOVERED;
> +
> +err_data:
> +	vfio_device_put(device);
> +err_dev:
> +	return err;
> +}
> +
>  static const struct pci_error_handlers vfio_err_handlers = {
>  	.error_detected = vfio_pci_aer_err_detected,
> +	.slot_reset = vfio_pci_aer_slot_reset,
>  };
>  
>  static struct pci_driver vfio_pci_driver = {
> diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c
> index 1c46045..270d568 100644
> --- a/drivers/vfio/pci/vfio_pci_intrs.c
> +++ b/drivers/vfio/pci/vfio_pci_intrs.c
> @@ -611,6 +611,17 @@ static int vfio_pci_set_err_trigger(struct vfio_pci_device *vdev,
>  					       count, flags, data);
>  }
>  
> +static int vfio_pci_set_non_fatal_err_trigger(struct vfio_pci_device *vdev,
> +				    unsigned index, unsigned start,
> +				    unsigned count, uint32_t flags, void *data)
> +{
> +	if (index != VFIO_PCI_NON_FATAL_ERR_IRQ_INDEX || start != 0 || count > 1)
> +		return -EINVAL;
> +
> +	return vfio_pci_set_ctx_trigger_single(&vdev->non_fatal_err_trigger,
> +					       count, flags, data);
> +}
> +
>  static int vfio_pci_set_req_trigger(struct vfio_pci_device *vdev,
>  				    unsigned index, unsigned start,
>  				    unsigned count, uint32_t flags, void *data)
> @@ -664,6 +675,14 @@ int vfio_pci_set_irqs_ioctl(struct vfio_pci_device *vdev, uint32_t flags,
>  			break;
>  		}
>  		break;
> +	case VFIO_PCI_NON_FATAL_ERR_IRQ_INDEX:
> +		switch (flags & VFIO_IRQ_SET_ACTION_TYPE_MASK) {
> +		case VFIO_IRQ_SET_ACTION_TRIGGER:
> +			if (pci_is_pcie(vdev->pdev))
> +				func = vfio_pci_set_non_fatal_err_trigger;
> +			break;
> +		}
> +		break;
>  	case VFIO_PCI_REQ_IRQ_INDEX:
>  		switch (flags & VFIO_IRQ_SET_ACTION_TYPE_MASK) {
>  		case VFIO_IRQ_SET_ACTION_TRIGGER:
> diff --git a/drivers/vfio/pci/vfio_pci_private.h b/drivers/vfio/pci/vfio_pci_private.h
> index f561ac1..d30f8a3 100644
> --- a/drivers/vfio/pci/vfio_pci_private.h
> +++ b/drivers/vfio/pci/vfio_pci_private.h
> @@ -93,6 +93,7 @@ struct vfio_pci_device {
>  	struct pci_saved_state	*pci_saved_state;
>  	int			refcnt;
>  	struct eventfd_ctx	*err_trigger;
> +	struct eventfd_ctx	*non_fatal_err_trigger;
>  	struct eventfd_ctx	*req_trigger;
>  	struct list_head	dummy_resources_list;
>  };
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index 519eff3..affa973 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -443,6 +443,7 @@ enum {
>  	VFIO_PCI_MSIX_IRQ_INDEX,
>  	VFIO_PCI_ERR_IRQ_INDEX,
>  	VFIO_PCI_REQ_IRQ_INDEX,
> +	VFIO_PCI_NON_FATAL_ERR_IRQ_INDEX,
>  	VFIO_PCI_NUM_IRQS
>  };
>  
> -- 
> 1.8.3.1
> 
>