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

From: Cao jin
Date: Mon Feb 27 2017 - 20:27:04 EST



On 02/28/2017 12:16 AM, Michael S. Tsirkin wrote:
> 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.
>

Ok. I didn' see [PATCH v3], I guess I am not CCed.

>> 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.

On this topic, I am really bewildered for a while, thanks for clarification.

--
Sincerely,
Cao jin

>
>> 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
>>
>>
>
>
> .
>