linux-kernel - [PATCH v1 4/6] vfio-pci/zdev: Setup a zpci memory region for error information

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Message-ID: <20250813170821.1115-5-alifm@linux.ibm.com>
Date: Wed, 13 Aug 2025 10:08:18 -0700
From: Farhan Ali <alifm@...ux.ibm.com>
To: linux-s390@...r.kernel.org, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc: schnelle@...ux.ibm.com, mjrosato@...ux.ibm.com, alifm@...ux.ibm.com,
        alex.williamson@...hat.com
Subject: [PATCH v1 4/6] vfio-pci/zdev: Setup a zpci memory region for error information

For zpci devices, we have platform specific error information.
To enable recovery for passthrough devices, we want to expose
this error information to user space. We can expose this information
via a device specific (read only) memory region.

Signed-off-by: Farhan Ali <alifm@...ux.ibm.com>
---
 drivers/vfio/pci/vfio_pci_zdev.c | 76 ++++++++++++++++++++++++++++++++
 include/uapi/linux/vfio.h        |  2 +
 include/uapi/linux/vfio_zdev.h   |  5 +++
 3 files changed, 83 insertions(+)

diff --git a/drivers/vfio/pci/vfio_pci_zdev.c b/drivers/vfio/pci/vfio_pci_zdev.c
index 2be37eab9279..818235b28caa 100644
--- a/drivers/vfio/pci/vfio_pci_zdev.c
+++ b/drivers/vfio/pci/vfio_pci_zdev.c
@@ -141,15 +141,91 @@ int vfio_pci_info_zdev_add_caps(struct vfio_pci_core_device *vdev,
 	return ret;
 }
 
+static ssize_t vfio_pci_zdev_read_err_region(struct vfio_pci_core_device *vdev,
+					    char __user *buf, size_t count,
+					    loff_t *ppos, bool iswrite)
+{
+	struct zpci_dev *zdev = to_zpci(vdev->pdev);
+	struct zpci_ccdf_err err;
+	struct vfio_device_zpci_err_region *region;
+	unsigned int i = VFIO_PCI_OFFSET_TO_INDEX(*ppos) - VFIO_PCI_NUM_REGIONS;
+	int head = 0;
+	loff_t pos = *ppos & VFIO_PCI_OFFSET_MASK;
+
+	region = vdev->region[i].data;
+
+	if (!zdev)
+		return -ENODEV;
+
+	if (pos + count > vdev->region[i].size || iswrite)
+		return -EINVAL;
+
+	mutex_lock(&zdev->pending_errs_lock);
+	if (zdev->pending_errs.count) {
+		head = zdev->pending_errs.head % ZPCI_ERR_PENDING_MAX;
+		err = zdev->pending_errs.err[head];
+		region->pec = err.pec;
+		zdev->pending_errs.head++;
+		zdev->pending_errs.count--;
+		region->pending_errors = zdev->pending_errs.count;
+	}
+	mutex_unlock(&zdev->pending_errs_lock);
+
+	if (copy_to_user(buf, (void *)region + pos, count))
+		count = -EFAULT;
+
+	return count;
+}
+
+static void vfio_pci_zdev_release_err_region(struct vfio_pci_core_device *vdev,
+					     struct vfio_pci_region *region)
+{
+	struct vfio_device_zpci_err_region *err_region = region->data;
+
+	kfree(err_region);
+}
+
+static const struct vfio_pci_regops vfio_pci_zdev_err_regops = {
+	.rw = vfio_pci_zdev_read_err_region,
+	.release = vfio_pci_zdev_release_err_region
+};
+
+static int vfio_pci_zdev_setup_err_region(struct vfio_pci_core_device *vdev)
+{
+	struct vfio_device_zpci_err_region *region;
+	int ret = 0;
+
+	region = kzalloc(sizeof(*region), GFP_KERNEL);
+	if (!region)
+		return -ENOMEM;
+
+	ret = vfio_pci_core_register_dev_region(vdev,
+		PCI_VENDOR_ID_IBM | VFIO_REGION_TYPE_PCI_VENDOR_TYPE,
+		VFIO_REGION_SUBTYPE_IBM_ZPCI_ERROR_REGION,
+		&vfio_pci_zdev_err_regops,
+		sizeof(*region), VFIO_REGION_INFO_FLAG_READ, region);
+
+	if (ret)
+		kfree(region);
+
+
+	return ret;
+}
+
 int vfio_pci_zdev_open_device(struct vfio_pci_core_device *vdev)
 {
 	struct zpci_dev *zdev = to_zpci(vdev->pdev);
+	int ret;
 
 	if (!zdev)
 		return -ENODEV;
 
 	zdev->mediated_recovery = true;
 
+	ret = vfio_pci_zdev_setup_err_region(vdev);
+	if (ret)
+		return ret;
+
 	if (!vdev->vdev.kvm)
 		return 0;
 
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index 75100bf009ba..452b87f3672e 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -369,6 +369,8 @@ struct vfio_region_info_cap_type {
  */
 #define VFIO_REGION_SUBTYPE_IBM_NVLINK2_ATSD	(1)
 
+#define VFIO_REGION_SUBTYPE_IBM_ZPCI_ERROR_REGION (2)
+
 /* sub-types for VFIO_REGION_TYPE_GFX */
 #define VFIO_REGION_SUBTYPE_GFX_EDID            (1)
 
diff --git a/include/uapi/linux/vfio_zdev.h b/include/uapi/linux/vfio_zdev.h
index 77f2aff1f27e..bcd06f334a42 100644
--- a/include/uapi/linux/vfio_zdev.h
+++ b/include/uapi/linux/vfio_zdev.h
@@ -82,4 +82,9 @@ struct vfio_device_info_cap_zpci_pfip {
 	__u8 pfip[];
 };
 
+struct vfio_device_zpci_err_region {
+	__u16 pec;
+	int pending_errors;
+};
+
 #endif
-- 
2.43.0