[PATCH v8 5/9] s390/pci: Update the logic for detecting passthrough device

Farhan Ali
2026-01-22T19:45:02Z

We can now have userspace drivers (vfio-pci based) on s390x. The userspace
drivers will not have any KVM fd and so no kzdev associated with them. So
we need to update the logic for detecting passthrough devices to not depend
on struct kvm_zdev.

Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Farhan Ali <alifm@linux.ibm.com>
---
arch/s390/include/asm/pci.h | 1 +
arch/s390/pci/pci_event.c | 14 ++++----------
drivers/vfio/pci/vfio_pci_zdev.c | 9 ++++++++-
3 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/arch/s390/include/asm/pci.h b/arch/s390/include/asm/pci.h
index c0ff19dab580..ec8a772bf526 100644
--- a/arch/s390/include/asm/pci.h
+++ b/arch/s390/include/asm/pci.h
@@ -171,6 +171,7 @@ struct zpci_dev {

char res_name[16];
bool mio_capable;
+ bool mediated_recovery;
struct zpci_bar_struct bars[PCI_STD_NUM_BARS];

u64 start_dma; /* Start of available DMA addresses */
diff --git a/arch/s390/pci/pci_event.c b/arch/s390/pci/pci_event.c
index 839bd91c056e..de504925f709 100644
--- a/arch/s390/pci/pci_event.c
+++ b/arch/s390/pci/pci_event.c
@@ -60,16 +60,10 @@ static inline bool ers_result_indicates_abort(pci_ers_result_t ers_res)
}
}

-static bool is_passed_through(struct pci_dev *pdev)
+static bool needs_mediated_recovery(struct pci_dev *pdev)
{
struct zpci_dev *zdev = to_zpci(pdev);
- bool ret;
-
- mutex_lock(&zdev->kzdev_lock);
- ret = !!zdev->kzdev;
- mutex_unlock(&zdev->kzdev_lock);
-
- return ret;
+ return zdev->mediated_recovery;
}

static bool is_driver_supported(struct pci_driver *driver)
@@ -194,7 +188,7 @@ static pci_ers_result_t zpci_event_attempt_error_recovery(struct pci_dev *pdev)
}
pdev->error_state = pci_channel_io_frozen;

- if (is_passed_through(pdev)) {
+ if (needs_mediated_recovery(pdev)) {
pr_info("%s: Cannot be recovered in the host because it is a pass-through device\n",
pci_name(pdev));
status_str = "failed (pass-through)";
@@ -279,7 +273,7 @@ static void zpci_event_io_failure(struct pci_dev *pdev, pci_channel_state_t es)
* we will inject the error event and let the guest recover the device
* itself.
*/
- if (is_passed_through(pdev))
+ if (needs_mediated_recovery(pdev))
goto out;
driver = to_pci_driver(pdev->dev.driver);
if (driver && driver->err_handler && driver->err_handler->error_detected)
diff --git a/drivers/vfio/pci/vfio_pci_zdev.c b/drivers/vfio/pci/vfio_pci_zdev.c
index 0990fdb146b7..a7bc23ce8483 100644
--- a/drivers/vfio/pci/vfio_pci_zdev.c
+++ b/drivers/vfio/pci/vfio_pci_zdev.c
@@ -148,6 +148,8 @@ int vfio_pci_zdev_open_device(struct vfio_pci_core_device *vdev)
if (!zdev)
return -ENODEV;

+ zdev->mediated_recovery = true;
+
if (!vdev->vdev.kvm)
return 0;

@@ -161,7 +163,12 @@ void vfio_pci_zdev_close_device(struct vfio_pci_core_device *vdev)
{
struct zpci_dev *zdev = to_zpci(vdev->pdev);

- if (!zdev || !vdev->vdev.kvm)
+ if (!zdev)
+ return;
+
+ zdev->mediated_recovery = false;
+
+ if (!vdev->vdev.kvm)
return;

if (zpci_kvm_hook.kvm_unregister)
--
2.43.0