[PATCH v9 7/9] vfio-pci/zdev: Add a device feature for error information

[Farhan Ali]

For zPCI devices, we have platform specific error information. The platform
firmware provides this error information to the operating system in an
architecture specific mechanism. To enable recovery from userspace for
these devices, we want to expose this error information to userspace. Add a
new device feature to expose this information.

Signed-off-by: Farhan Ali <alifm@xxxxxxxxxxxxx>
---
 drivers/vfio/pci/vfio_pci_core.c |  2 ++
 drivers/vfio/pci/vfio_pci_priv.h |  9 ++++++++
 drivers/vfio/pci/vfio_pci_zdev.c | 36 ++++++++++++++++++++++++++++++++
 include/uapi/linux/vfio.h        | 17 +++++++++++++++
 4 files changed, 64 insertions(+)

diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
index 72c33b399800..d2cb498c026b 100644
--- a/drivers/vfio/pci/vfio_pci_core.c
+++ b/drivers/vfio/pci/vfio_pci_core.c
@@ -1535,6 +1535,8 @@ int vfio_pci_core_ioctl_feature(struct vfio_device *device, u32 flags,
 		return vfio_pci_core_feature_token(vdev, flags, arg, argsz);
 	case VFIO_DEVICE_FEATURE_DMA_BUF:
 		return vfio_pci_core_feature_dma_buf(vdev, flags, arg, argsz);
+	case VFIO_DEVICE_FEATURE_ZPCI_ERROR:
+		return vfio_pci_zdev_feature_err(device, flags, arg, argsz);
 	default:
 		return -ENOTTY;
 	}
diff --git a/drivers/vfio/pci/vfio_pci_priv.h b/drivers/vfio/pci/vfio_pci_priv.h
index 27ac280f00b9..eed69926d8a1 100644
--- a/drivers/vfio/pci/vfio_pci_priv.h
+++ b/drivers/vfio/pci/vfio_pci_priv.h
@@ -89,6 +89,8 @@ int vfio_pci_info_zdev_add_caps(struct vfio_pci_core_device *vdev,
 				struct vfio_info_cap *caps);
 int vfio_pci_zdev_open_device(struct vfio_pci_core_device *vdev);
 void vfio_pci_zdev_close_device(struct vfio_pci_core_device *vdev);
+int vfio_pci_zdev_feature_err(struct vfio_device *device, u32 flags,
+			      void __user *arg, size_t argsz);
 #else
 static inline int vfio_pci_info_zdev_add_caps(struct vfio_pci_core_device *vdev,
 					      struct vfio_info_cap *caps)
@@ -103,6 +105,13 @@ static inline int vfio_pci_zdev_open_device(struct vfio_pci_core_device *vdev)
 
 static inline void vfio_pci_zdev_close_device(struct vfio_pci_core_device *vdev)
 {}
+
+static inline int vfio_pci_zdev_feature_err(struct vfio_device *device,
+					    u32 flags, void __user *arg,
+					    size_t argsz)
+{
+	return -ENODEV;
+}
 #endif
 
 static inline bool vfio_pci_is_vga(struct pci_dev *pdev)
diff --git a/drivers/vfio/pci/vfio_pci_zdev.c b/drivers/vfio/pci/vfio_pci_zdev.c
index 2be37eab9279..d2748dd67c55 100644
--- a/drivers/vfio/pci/vfio_pci_zdev.c
+++ b/drivers/vfio/pci/vfio_pci_zdev.c
@@ -141,6 +141,42 @@ int vfio_pci_info_zdev_add_caps(struct vfio_pci_core_device *vdev,
 	return ret;
 }
 
+int vfio_pci_zdev_feature_err(struct vfio_device *device, u32 flags,
+			      void __user *arg, size_t argsz)
+{
+	struct vfio_device_feature_zpci_err err;
+	struct vfio_pci_core_device *vdev;
+	struct zpci_dev *zdev;
+	int head = 0;
+	int ret;
+
+	vdev = container_of(device, struct vfio_pci_core_device, vdev);
+	zdev = to_zpci(vdev->pdev);
+	if (!zdev)
+		return -ENODEV;
+
+	ret = vfio_check_feature(flags, argsz, VFIO_DEVICE_FEATURE_GET,
+				 sizeof(err));
+	if (ret != 1)
+		return ret;
+
+	mutex_lock(&zdev->pending_errs_lock);
+	if (zdev->pending_errs.count) {
+		head = zdev->pending_errs.head % ZPCI_ERR_PENDING_MAX;
+		err.pec = zdev->pending_errs.err[head].pec;
+		zdev->pending_errs.head++;
+		zdev->pending_errs.count--;
+		err.pending_errors = zdev->pending_errs.count;
+	}
+	mutex_unlock(&zdev->pending_errs_lock);
+
+	err.version = 1;
+	if (copy_to_user(arg, &err, sizeof(err)))
+		return -EFAULT;
+
+	return 0;
+}
+
 int vfio_pci_zdev_open_device(struct vfio_pci_core_device *vdev)
 {
 	struct zpci_dev *zdev = to_zpci(vdev->pdev);
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index bb7b89330d35..21b1473e4779 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -1510,6 +1510,23 @@ struct vfio_device_feature_dma_buf {
 	struct vfio_region_dma_range dma_ranges[] __counted_by(nr_ranges);
 };
 
+/**
+ * VFIO_DEVICE_FEATURE_ZPCI_ERROR feature provides PCI error information to
+ * userspace for vfio-pci devices on s390x. On s390x PCI error recovery involves
+ * platform firmware and notification to operating system is done by
+ * architecture specific mechanism.  Exposing this information to userspace
+ * allows userspace to take appropriate actions to handle an error on the
+ * device.
+ */
+
+struct vfio_device_feature_zpci_err {
+	__u8 version;
+	__u8 pending_errors;
+	__u16 pec;
+};
+
+#define VFIO_DEVICE_FEATURE_ZPCI_ERROR 12
+
 /* -------- API for Type1 VFIO IOMMU -------- */
 
 /**
-- 
2.43.0