[Qemu-devel] [PATCH v5] vfio error recovery: kernel support

[Cao jin]

From: "Michael S. Tsirkin" <address@hidden>

0. What happens now (PCIE AER only)
   Fatal errors cause a link reset. Non fatal errors don't.
   All errors stop the QEMU guest eventually, but not immediately,
   because it's detected and reported asynchronously.
   Interrupts are forwarded as usual.
   Correctable errors are not reported to user at all.

   Note:
   PPC EEH is different, but this approach won' affect EEH, because
   EEH treat all errors as fatal ones in AER, will still signal user
   via the legacy eventfd. And all devices/functions in a PE belongs to
   the same IOMMU group, so the slot_reset handler in this approach
   won't affect EEH either.

1. Correctable errors
   Hardware can correct these errors without software intervention,
   clear the error status is enough, this is what already done now.
   No need to recover it, nothing changed, leave it as it is.

2. Fatal errors
   They will induce a link reset. This is troublesome when user is
   a QEMU guest. This approach doens't touch the existing mechanism.

3. Non-fatal errors
   Before, they are signalled to user the same as fatal ones. In this approach,
   a new eventfd is introduced only for non-fatal error notification. By
   splitting non-fatal ones out, it will benefit AER recovery of a QEMU guest
   user by reporting them to guest saparately.

   To maintain backwards compatibility with userspace, non-fatal errors
   will continue to trigger via the existing error interrupt index if a
   non-fatal signaling mechanism has not been registered.

   Note:
   In case of a multi-function device which has different device driver
   for each of them, and one of the functions is bound to vfio while
   others doesn't(i.e., functions belong to different IOMMU group), a new
   slot_reset handler & another new eventfd are introduced. This is
   useful when device driver wants a slot reset while vfio-pci doesn't,
   which means vfio-pci device will got a passive reset. Signal user
   via another new eventfd names passive_reset_trigger, this helps to
   avoid signalling user twice via the same legacy error trigger.

For the original design and discussion, refer:
https://www.spinics.net/lists/linux-virtualization/msg29843.html


Signed-off-by: Michael S. Tsirkin <address@hidden>
Signed-off-by: Cao jin <address@hidden>
---

v5 changelog:
1. Add another new eventfd passive_reset_trigger & the boilerplate code,
   used in slot_reset. Add comment for slot_reset().
2. Rewrite the commit log.

 drivers/vfio/pci/vfio_pci.c         | 49 +++++++++++++++++++++++++++++++++++--
 drivers/vfio/pci/vfio_pci_intrs.c   | 38 ++++++++++++++++++++++++++++
 drivers/vfio/pci/vfio_pci_private.h |  2 ++
 include/uapi/linux/vfio.h           |  2 ++
 4 files changed, 89 insertions(+), 2 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index 324c52e..375ba20 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -441,7 +441,9 @@ 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 ||
+                  irq_type == VFIO_PCI_PASSIVE_RESET_IRQ_INDEX) {
                if (pci_is_pcie(vdev->pdev))
                        return 1;
        } else if (irq_type == VFIO_PCI_REQ_IRQ_INDEX) {
@@ -796,6 +798,8 @@ 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:
+               case VFIO_PCI_PASSIVE_RESET_IRQ_INDEX:
                        if (pci_is_pcie(vdev->pdev))
                                break;
                /* pass thru to return error */
@@ -1282,7 +1286,9 @@ 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 +1298,47 @@ static pci_ers_result_t vfio_pci_aer_err_detected(struct 
pci_dev *pdev,
        return PCI_ERS_RESULT_CAN_RECOVER;
 }
 
+/*
+ * In case of a function/device is bound to vfio, while other collateral ones
+ * are still controlled by device driver(i.e., they belongs to different iommu
+ * group), and device driver want a slot reset when seeing AER errors while
+ * vfio pci doesn't, signal user via with proprietary eventfd in precedence to
+ * the legacy one.
+ */
+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->passive_reset_trigger)
+               eventfd_signal(vdev->passive_reset_trigger, 1);
+       else 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..7157d85 100644
--- a/drivers/vfio/pci/vfio_pci_intrs.c
+++ b/drivers/vfio/pci/vfio_pci_intrs.c
@@ -611,6 +611,28 @@ 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_passive_reset_trigger(struct vfio_pci_device *vdev,
+                                   unsigned index, unsigned start,
+                                   unsigned count, uint32_t flags, void *data)
+{
+       if (index != VFIO_PCI_PASSIVE_RESET_IRQ_INDEX || start != 0 || count > 
1)
+               return -EINVAL;
+
+       return vfio_pci_set_ctx_trigger_single(&vdev->passive_reset_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 +686,22 @@ 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_PASSIVE_RESET_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_passive_reset_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..cbc4b88 100644
--- a/drivers/vfio/pci/vfio_pci_private.h
+++ b/drivers/vfio/pci/vfio_pci_private.h
@@ -93,6 +93,8 @@ 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      *passive_reset_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..26b4be0 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -443,6 +443,8 @@ 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_PASSIVE_RESET_IRQ_INDEX,
        VFIO_PCI_NUM_IRQS
 };
 
-- 
1.8.3.1