linux-kernel - [PATCH v1 5/6] vfio-pci/zdev: Perform platform specific function reset for zPCI

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Message-ID: <20250813170821.1115-6-alifm@linux.ibm.com>
Date: Wed, 13 Aug 2025 10:08:19 -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 5/6] vfio-pci/zdev: Perform platform specific function reset for zPCI

For zPCI devices we should drive a platform specific function reset
as part of VFIO_DEVICE_RESET. This reset is needed recover a zPCI device
in error state.

Signed-off-by: Farhan Ali <alifm@...ux.ibm.com>
---
 arch/s390/pci/pci.c              |  1 +
 drivers/vfio/pci/vfio_pci_core.c |  4 ++++
 drivers/vfio/pci/vfio_pci_priv.h |  5 ++++
 drivers/vfio/pci/vfio_pci_zdev.c | 39 ++++++++++++++++++++++++++++++++
 4 files changed, 49 insertions(+)

diff --git a/arch/s390/pci/pci.c b/arch/s390/pci/pci.c
index f795e05b5001..860a64993b58 100644
--- a/arch/s390/pci/pci.c
+++ b/arch/s390/pci/pci.c
@@ -788,6 +788,7 @@ int zpci_hot_reset_device(struct zpci_dev *zdev)
 
 	return rc;
 }
+EXPORT_SYMBOL_GPL(zpci_hot_reset_device);
 
 /**
  * zpci_create_device() - Create a new zpci_dev and add it to the zbus
diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
index 7dcf5439dedc..7220a22135a9 100644
--- a/drivers/vfio/pci/vfio_pci_core.c
+++ b/drivers/vfio/pci/vfio_pci_core.c
@@ -1227,6 +1227,10 @@ static int vfio_pci_ioctl_reset(struct vfio_pci_core_device *vdev,
 	 */
 	vfio_pci_set_power_state(vdev, PCI_D0);
 
+	ret = vfio_pci_zdev_reset(vdev);
+	if (ret && ret != -ENODEV)
+		return ret;
+
 	ret = pci_try_reset_function(vdev->pdev);
 	up_write(&vdev->memory_lock);
 
diff --git a/drivers/vfio/pci/vfio_pci_priv.h b/drivers/vfio/pci/vfio_pci_priv.h
index a9972eacb293..5288577b3170 100644
--- a/drivers/vfio/pci/vfio_pci_priv.h
+++ b/drivers/vfio/pci/vfio_pci_priv.h
@@ -86,6 +86,7 @@ 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_reset(struct vfio_pci_core_device *vdev);
 #else
 static inline int vfio_pci_info_zdev_add_caps(struct vfio_pci_core_device *vdev,
 					      struct vfio_info_cap *caps)
@@ -100,6 +101,10 @@ 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)
 {}
+int vfio_pci_zdev_reset(struct vfio_pci_core_device *vdev)
+{
+	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 818235b28caa..dd1919ccb3be 100644
--- a/drivers/vfio/pci/vfio_pci_zdev.c
+++ b/drivers/vfio/pci/vfio_pci_zdev.c
@@ -212,6 +212,45 @@ static int vfio_pci_zdev_setup_err_region(struct vfio_pci_core_device *vdev)
 	return ret;
 }
 
+int vfio_pci_zdev_reset(struct vfio_pci_core_device *vdev)
+{
+	struct zpci_dev *zdev = to_zpci(vdev->pdev);
+	int rc = -EIO;
+
+	if (!zdev)
+		return -ENODEV;
+
+	/*
+	 * If we can't get the zdev->state_lock the device state is
+	 * currently undergoing a transition and we bail out - just
+	 * the same as if the device's state is not configured at all.
+	 */
+	if (!mutex_trylock(&zdev->state_lock))
+		return rc;
+
+	/* We can reset only if the function is configured */
+	if (zdev->state != ZPCI_FN_STATE_CONFIGURED)
+		goto out;
+
+	rc = zpci_hot_reset_device(zdev);
+	if (rc != 0)
+		goto out;
+
+	if (!vdev->pci_saved_state) {
+		pci_err(vdev->pdev, "No saved available for the device");
+		rc = -EIO;
+		goto out;
+	}
+
+	pci_dev_lock(vdev->pdev);
+	pci_load_saved_state(vdev->pdev, vdev->pci_saved_state);
+	pci_restore_state(vdev->pdev);
+	pci_dev_unlock(vdev->pdev);
+out:
+	mutex_unlock(&zdev->state_lock);
+	return rc;
+}
+
 int vfio_pci_zdev_open_device(struct vfio_pci_core_device *vdev)
 {
 	struct zpci_dev *zdev = to_zpci(vdev->pdev);
-- 
2.43.0