[PATCH] vfio/pci: Support error recovery
From: Cao jin
Date: Sun Nov 27 2016 - 06:31:07 EST
It is user space driver's or device-specific driver's(in guest) responsbility
to do a serious recovery when error happened. Link-reset is one part of
recovery, when pci device is assigned to VM via vfio, link-reset will do
twice in host & guest separately, which will cause many trouble for a
successful recovery, so, disable the vfio-pci's link-reset in aer driver
in host, this is a keypoint for guest to do error recovery successfully.
CC: alex.williamson@xxxxxxxxxx
CC: mst@xxxxxxxxxx
Signed-off-by: Cao jin <caoj.fnst@xxxxxxxxxxxxxx>
---
This is actually a RFC version(has debug lines left), and has minor changes in
aer driver, so I think maybe it is better not to CC pci guys in this round.
Later will do.
drivers/pci/pcie/aer/aerdrv_core.c | 12 ++++++-
drivers/vfio/pci/vfio_pci.c | 63 +++++++++++++++++++++++++++++++++++--
drivers/vfio/pci/vfio_pci_private.h | 2 ++
3 files changed, 74 insertions(+), 3 deletions(-)
diff --git a/drivers/pci/pcie/aer/aerdrv_core.c b/drivers/pci/pcie/aer/aerdrv_core.c
index 521e39c..289fb8e 100644
--- a/drivers/pci/pcie/aer/aerdrv_core.c
+++ b/drivers/pci/pcie/aer/aerdrv_core.c
@@ -496,7 +496,17 @@ static void do_recovery(struct pci_dev *dev, int severity)
"error_detected",
report_error_detected);
- if (severity == AER_FATAL) {
+ /* vfio-pci as a general meta driver, it actually couldn't do any real
+ * recovery for device. It is user space driver, or device-specific
+ * driver in guest who should take care of the serious error recovery,
+ * link reset actually is one part of whole recovery. Doing reset_link
+ * in aer driver of host kernel for vfio-pci devices will cause many
+ * trouble for user space driver or guest's device-specific driver,
+ * for example: the serious recovery often need to read register in
+ * config space, but if register reading happens during link-resetting,
+ * it is quite possible to return invalid value like all F's, which
+ * will result in unpredictable error. */
+ if (severity == AER_FATAL && strcmp(dev->driver->name, "vfio-pci")) {
result = reset_link(dev);
if (result != PCI_ERS_RESULT_RECOVERED)
goto failed;
diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index 712a849..aefd751 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -535,6 +535,15 @@ static long vfio_pci_ioctl(void *device_data,
struct vfio_pci_device *vdev = device_data;
unsigned long minsz;
+ if (vdev->aer_recovering && (cmd == VFIO_DEVICE_SET_IRQS ||
+ cmd == VFIO_DEVICE_RESET || cmd == VFIO_DEVICE_PCI_HOT_RESET)) {
+ int ret;
+ ret = wait_for_completion_interruptible(
+ &vdev->aer_error_completion);
+ if (ret)
+ return ret;
+ }
+
if (cmd == VFIO_DEVICE_GET_INFO) {
struct vfio_device_info info;
@@ -1117,6 +1126,7 @@ static int vfio_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
vdev->irq_type = VFIO_PCI_NUM_IRQS;
mutex_init(&vdev->igate);
spin_lock_init(&vdev->irqlock);
+ init_completion(&vdev->aer_error_completion);
ret = vfio_add_group_dev(&pdev->dev, &vfio_pci_ops, vdev);
if (ret) {
@@ -1176,6 +1186,9 @@ static pci_ers_result_t vfio_pci_aer_err_detected(struct pci_dev *pdev,
{
struct vfio_pci_device *vdev;
struct vfio_device *device;
+ u32 uncor_status = 0;
+ unsigned int aer_cap_offset = 0;
+ int ret;
device = vfio_device_get_from_dev(&pdev->dev);
if (device == NULL)
@@ -1187,10 +1200,30 @@ static pci_ers_result_t vfio_pci_aer_err_detected(struct pci_dev *pdev,
return PCI_ERS_RESULT_DISCONNECT;
}
+ /* get device's uncorrectable error status as soon as possible,
+ * and signal it to user space. The later we read it, the possibility
+ * the register value is mangled grows. */
+ aer_cap_offset = pci_find_ext_capability(vdev->pdev, PCI_EXT_CAP_ID_ERR);
+ ret = pci_read_config_dword(vdev->pdev, aer_cap_offset +
+ PCI_ERR_UNCOR_STATUS, &uncor_status);
+ if (ret)
+ return PCI_ERS_RESULT_DISCONNECT;
+
+ pr_err("device %d got AER detect notification. uncorrectable error status = 0x%x\n", pdev->devfn, uncor_status);//to be removed
mutex_lock(&vdev->igate);
+
+ vdev->aer_recovering = true;
+ reinit_completion(&vdev->aer_error_completion);
+
+ /* suspend config space access from user space,
+ * when vfio-pci's error recovery process is on */
+ pci_cfg_access_trylock(vdev->pdev);
- if (vdev->err_trigger)
- eventfd_signal(vdev->err_trigger, 1);
+ if (vdev->err_trigger && uncor_status) {
+ pr_err("device %d signal uncor status to user space", pdev->devfn);//may be removed
+ /* signal uncorrectable error status to user space */
+ eventfd_signal(vdev->err_trigger, uncor_status);
+ }
mutex_unlock(&vdev->igate);
@@ -1199,8 +1232,34 @@ static pci_ers_result_t vfio_pci_aer_err_detected(struct pci_dev *pdev,
return PCI_ERS_RESULT_CAN_RECOVER;
}
+static void vfio_pci_aer_resume(struct pci_dev *pdev)
+{
+ struct vfio_pci_device *vdev;
+ struct vfio_device *device;
+
+ device = vfio_device_get_from_dev(&pdev->dev);
+ if (device == NULL)
+ return;
+
+ vdev = vfio_device_data(device);
+ if (vdev == NULL) {
+ vfio_device_put(device);
+ return;
+ }
+
+ /* vfio-pci's error recovery is done, time to
+ * resume pci config space's accesses */
+ pci_cfg_access_unlock(vdev->pdev);
+
+ vdev->aer_recovering = false;
+ complete_all(&vdev->aer_error_completion);
+
+ vfio_device_put(device);
+}
+
static const struct pci_error_handlers vfio_err_handlers = {
.error_detected = vfio_pci_aer_err_detected,
+ .resume = vfio_pci_aer_resume,
};
static struct pci_driver vfio_pci_driver = {
diff --git a/drivers/vfio/pci/vfio_pci_private.h b/drivers/vfio/pci/vfio_pci_private.h
index 8a7d546..ebf1041 100644
--- a/drivers/vfio/pci/vfio_pci_private.h
+++ b/drivers/vfio/pci/vfio_pci_private.h
@@ -83,6 +83,8 @@ struct vfio_pci_device {
bool bardirty;
bool has_vga;
bool needs_reset;
+ bool aer_recovering;
+ struct completion aer_error_completion;
struct pci_saved_state *pci_saved_state;
int refcnt;
struct eventfd_ctx *err_trigger;
--
1.8.3.1