[PATCH v15 5/7] vfio-pci/zdev: Add a device feature for error information

[Farhan Ali <alifm@linux.ibm.com>]

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.

Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>
Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Farhan Ali <alifm@linux.ibm.com>
---
 arch/s390/include/asm/pci.h      |  2 ++
 arch/s390/pci/pci_event.c        | 19 ++++++++++++++++
 drivers/vfio/pci/vfio_pci_core.c |  2 ++
 drivers/vfio/pci/vfio_pci_priv.h |  9 ++++++++
 drivers/vfio/pci/vfio_pci_zdev.c | 39 ++++++++++++++++++++++++++++++++
 include/uapi/linux/vfio.h        | 30 ++++++++++++++++++++++++
 6 files changed, 101 insertions(+)

diff --git a/arch/s390/include/asm/pci.h b/arch/s390/include/asm/pci.h
index 016386f7ef4a..88a125b92bdd 100644
--- a/arch/s390/include/asm/pci.h
+++ b/arch/s390/include/asm/pci.h
@@ -364,6 +364,8 @@ int zpci_clear_error_state(struct zpci_dev *zdev);
 int zpci_reset_load_store_blocked(struct zpci_dev *zdev);
 void zpci_start_mediated_recovery(struct zpci_dev *zdev);
 void zpci_stop_mediated_recovery(struct zpci_dev *zdev);
+int zpci_get_pending_error(struct zpci_dev *zdev,
+			   struct zpci_ccdf_err *ccdf);
 
 #ifdef CONFIG_NUMA
 
diff --git a/arch/s390/pci/pci_event.c b/arch/s390/pci/pci_event.c
index 41547c54076f..fc4b51bc4c3c 100644
--- a/arch/s390/pci/pci_event.c
+++ b/arch/s390/pci/pci_event.c
@@ -74,6 +74,25 @@ static void zpci_store_pci_error(struct pci_dev *pdev,
 	zdev->pending_errs.count++;
 }
 
+int zpci_get_pending_error(struct zpci_dev *zdev,
+			    struct zpci_ccdf_err *ccdf)
+{
+	int head = 0;
+
+	guard(mutex)(&zdev->pending_errs_lock);
+
+	if (!zdev->pending_errs.count)
+		return -ENOMSG;
+
+	head = zdev->pending_errs.head % ZPCI_ERR_PENDING_MAX;
+	memcpy(ccdf, &zdev->pending_errs.err[head],
+		sizeof(struct zpci_ccdf_err));
+	zdev->pending_errs.head++;
+	zdev->pending_errs.count--;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(zpci_get_pending_error);
+
 void zpci_start_mediated_recovery(struct zpci_dev *zdev)
 {
 	guard(mutex)(&zdev->pending_errs_lock);
diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
index 3f8d093aacf8..f47a49ca67fa 100644
--- a/drivers/vfio/pci/vfio_pci_core.c
+++ b/drivers/vfio/pci/vfio_pci_core.c
@@ -1534,6 +1534,8 @@ 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 fca9d0dfac90..4e7162234a2e 100644
--- a/drivers/vfio/pci/vfio_pci_priv.h
+++ b/drivers/vfio/pci/vfio_pci_priv.h
@@ -93,6 +93,8 @@ 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)
@@ -107,6 +109,13 @@ 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 -ENOTTY;
+}
 #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 78a28db00c6d..cc148123a97b 100644
--- a/drivers/vfio/pci/vfio_pci_zdev.c
+++ b/drivers/vfio/pci/vfio_pci_zdev.c
@@ -141,6 +141,45 @@ 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_ccdf_err ccdf = {};
+	struct zpci_dev *zdev;
+	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;
+
+	ret = zpci_get_pending_error(zdev, &ccdf);
+	if (ret)
+		return ret;
+
+	err.fh = ccdf.fh;
+	err.fid = ccdf.fid;
+	err.ett = ccdf.ett;
+	err.mvn = ccdf.mvn;
+	err.dmaas = ccdf.dmaas;
+	err.q = ccdf.q;
+	err.rw = ccdf.rw;
+	err.faddr = ccdf.faddr;
+	err.pec = ccdf.pec;
+
+	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 5de618a3a5ee..3eead86a00ab 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -1534,6 +1534,36 @@ struct vfio_device_feature_dma_buf {
  */
 #define VFIO_DEVICE_FEATURE_MIG_PRECOPY_INFOv2  12
 
+/**
+ * VFIO_DEVICE_FEATURE_ZPCI_ERROR feature provides PCI error information to
+ * userspace for vfio-pci devices on s390. On s390, PCI error recovery
+ * involves platform firmware and notification to operating systems is done
+ * by architecture specific mechanism. Exposing this information to
+ * userspace allows it to take appropriate actions to handle an
+ * error on the device. The ioctl returns -ENOMSG if there are no pending
+ * PCI errors.
+ */
+
+struct vfio_device_feature_zpci_err {
+	__u32 feature_flags;		/* Indicate future features */
+	__u32 reserved1;
+	__u32 fh;			/* function handle */
+	__u32 fid;			/* function id */
+	__u32 ett		:  4;	/* expected table type */
+	__u32 mvn		: 12;	/* MSI vector number */
+	__u32 dmaas		:  8;	/* DMA address space */
+	__u32 reserved2		:  6;
+	__u32 q			:  1;	/* event qualifier */
+	__u32 rw		:  1;	/* read/write */
+	__u64 faddr;			/* failing address */
+	__u32 reserved3;
+	__u16 reserved4;
+	__u16 pec;			/* PCI event code */
+	__u8 reserved5[28];		/* Allow for future expansion */
+};
+
+#define VFIO_DEVICE_FEATURE_ZPCI_ERROR 13
+
 /* -------- API for Type1 VFIO IOMMU -------- */
 
 /**
-- 
2.43.0