* [PATCH v19 1/3] s390/pci: Store PCI error information for passthrough devices
2026-06-15 18:36 [PATCH v19 0/3] [VFIO] Error recovery for vfio-pci devices on s390x Farhan Ali
@ 2026-06-15 18:36 ` Farhan Ali
2026-06-15 18:47 ` sashiko-bot
2026-06-15 18:36 ` [PATCH v19 2/3] vfio-pci/zdev: Add a device feature for error information Farhan Ali
` (2 subsequent siblings)
3 siblings, 1 reply; 10+ messages in thread
From: Farhan Ali @ 2026-06-15 18:36 UTC (permalink / raw)
To: linux-s390, linux-kernel, linux-pci
Cc: helgaas, alex, alifm, schnelle, mjrosato
For a passthrough device we need co-operation from user space to recover
the device. This would require to bubble up any error information to user
space. Let's store this error information for passthrough devices, so it
can be retrieved later.
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: 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 | 30 ++++++++
arch/s390/pci/pci.c | 1 +
arch/s390/pci/pci_event.c | 118 ++++++++++++++++++-------------
drivers/vfio/pci/vfio_pci_zdev.c | 18 ++++-
4 files changed, 113 insertions(+), 54 deletions(-)
diff --git a/arch/s390/include/asm/pci.h b/arch/s390/include/asm/pci.h
index 5dcf35f0f325..016386f7ef4a 100644
--- a/arch/s390/include/asm/pci.h
+++ b/arch/s390/include/asm/pci.h
@@ -118,6 +118,32 @@ struct zpci_bus {
enum pci_bus_speed max_bus_speed;
};
+/* Content Code Description for PCI Function Error */
+struct zpci_ccdf_err {
+ 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 */
+} __packed;
+
+#define ZPCI_ERR_PENDING_MAX 4
+struct zpci_ccdf_pending {
+ bool mediated_recovery;
+ u8 count;
+ u8 head;
+ u8 tail;
+ struct zpci_ccdf_err err[ZPCI_ERR_PENDING_MAX];
+};
+
/* Private data per function */
struct zpci_dev {
struct zpci_bus *zbus;
@@ -192,6 +218,8 @@ struct zpci_dev {
struct iommu_domain *s390_domain; /* attached IOMMU domain */
struct kvm_zdev *kzdev;
struct mutex kzdev_lock;
+ struct zpci_ccdf_pending pending_errs;
+ struct mutex pending_errs_lock;
spinlock_t dom_lock; /* protect s390_domain change */
};
@@ -334,6 +362,8 @@ void zpci_debug_exit_device(struct zpci_dev *);
int zpci_report_error(struct pci_dev *, struct zpci_report_error_header *);
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);
#ifdef CONFIG_NUMA
diff --git a/arch/s390/pci/pci.c b/arch/s390/pci/pci.c
index 39bd2adfc240..2d377c2e194d 100644
--- a/arch/s390/pci/pci.c
+++ b/arch/s390/pci/pci.c
@@ -842,6 +842,7 @@ struct zpci_dev *zpci_create_device(u32 fid, u32 fh, enum zpci_state state)
mutex_init(&zdev->state_lock);
mutex_init(&zdev->fmb_lock);
mutex_init(&zdev->kzdev_lock);
+ mutex_init(&zdev->pending_errs_lock);
return zdev;
diff --git a/arch/s390/pci/pci_event.c b/arch/s390/pci/pci_event.c
index 839bd91c056e..8934b640a095 100644
--- a/arch/s390/pci/pci_event.c
+++ b/arch/s390/pci/pci_event.c
@@ -17,23 +17,6 @@
#include "pci_bus.h"
#include "pci_report.h"
-/* Content Code Description for PCI Function Error */
-struct zpci_ccdf_err {
- 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 : 6;
- u32 q : 1; /* event qualifier */
- u32 rw : 1; /* read/write */
- u64 faddr; /* failing address */
- u32 reserved3;
- u16 reserved4;
- u16 pec; /* PCI event code */
-} __packed;
-
/* Content Code Description for PCI Function Availability */
struct zpci_ccdf_avail {
u32 reserved1;
@@ -60,18 +43,6 @@ static inline bool ers_result_indicates_abort(pci_ers_result_t ers_res)
}
}
-static bool is_passed_through(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;
-}
-
static bool is_driver_supported(struct pci_driver *driver)
{
if (!driver || !driver->err_handler)
@@ -81,6 +52,49 @@ static bool is_driver_supported(struct pci_driver *driver)
return true;
}
+static int zpci_store_pci_error(struct pci_dev *pdev,
+ struct zpci_ccdf_err *ccdf)
+{
+ struct zpci_dev *zdev = to_zpci(pdev);
+ int i;
+
+ guard(mutex)(&zdev->pending_errs_lock);
+ if (!zdev->pending_errs.mediated_recovery)
+ return -EINVAL;
+
+ if (zdev->pending_errs.count >= ZPCI_ERR_PENDING_MAX) {
+ dev_warn_ratelimited(&pdev->dev,
+ "%s: Maximum number (%d) of pending error events queued\n",
+ pci_name(pdev),
+ ZPCI_ERR_PENDING_MAX);
+ return -ENOMEM;
+ }
+
+ i = zdev->pending_errs.tail % ZPCI_ERR_PENDING_MAX;
+ memcpy(&zdev->pending_errs.err[i], ccdf, sizeof(struct zpci_ccdf_err));
+ zdev->pending_errs.tail++;
+ zdev->pending_errs.count++;
+ return 0;
+}
+
+void zpci_start_mediated_recovery(struct zpci_dev *zdev)
+{
+ guard(mutex)(&zdev->pending_errs_lock);
+ zdev->pending_errs.mediated_recovery = true;
+}
+EXPORT_SYMBOL_GPL(zpci_start_mediated_recovery);
+
+void zpci_stop_mediated_recovery(struct zpci_dev *zdev)
+{
+ guard(mutex)(&zdev->pending_errs_lock);
+ zdev->pending_errs.mediated_recovery = false;
+ if (zdev->pending_errs.count)
+ pr_info("Unhandled PCI error events count=%d for PCI function 0x%x\n",
+ zdev->pending_errs.count, zdev->fid);
+ memset(&zdev->pending_errs, 0, sizeof(struct zpci_ccdf_pending));
+}
+EXPORT_SYMBOL_GPL(zpci_stop_mediated_recovery);
+
static pci_ers_result_t zpci_event_notify_error_detected(struct pci_dev *pdev,
struct pci_driver *driver)
{
@@ -175,12 +189,15 @@ static pci_ers_result_t zpci_event_do_reset(struct pci_dev *pdev,
* and the platform determines which functions are affected for
* multi-function devices.
*/
-static pci_ers_result_t zpci_event_attempt_error_recovery(struct pci_dev *pdev)
+static pci_ers_result_t zpci_event_attempt_error_recovery(struct pci_dev *pdev,
+ struct zpci_ccdf_err *ccdf)
{
pci_ers_result_t ers_res = PCI_ERS_RESULT_DISCONNECT;
struct zpci_dev *zdev = to_zpci(pdev);
+ bool mediated_recovery = false;
char *status_str = "success";
struct pci_driver *driver;
+ int rc;
/*
* Ensure that the PCI function is not removed concurrently, no driver
@@ -194,13 +211,6 @@ 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)) {
- 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)";
- goto out_unlock;
- }
-
driver = to_pci_driver(pdev->dev.driver);
if (!is_driver_supported(driver)) {
if (!driver) {
@@ -216,12 +226,24 @@ static pci_ers_result_t zpci_event_attempt_error_recovery(struct pci_dev *pdev)
goto out_unlock;
}
+ rc = zpci_store_pci_error(pdev, ccdf);
+ if (!rc || rc == -ENOMEM)
+ mediated_recovery = true;
+
ers_res = zpci_event_notify_error_detected(pdev, driver);
if (ers_result_indicates_abort(ers_res)) {
status_str = "failed (abort on detection)";
goto out_unlock;
}
+ if (mediated_recovery) {
+ pr_info("%s: Leaving recovery of pass-through device to user-space\n",
+ pci_name(pdev));
+ ers_res = PCI_ERS_RESULT_RECOVERED;
+ status_str = "in progress";
+ goto out_unlock;
+ }
+
if (ers_res != PCI_ERS_RESULT_NEED_RESET) {
ers_res = zpci_event_do_error_state_clear(pdev, driver);
if (ers_result_indicates_abort(ers_res)) {
@@ -266,25 +288,19 @@ static pci_ers_result_t zpci_event_attempt_error_recovery(struct pci_dev *pdev)
* @pdev: PCI function for which to report
* @es: PCI channel failure state to report
*/
-static void zpci_event_io_failure(struct pci_dev *pdev, pci_channel_state_t es)
+static void zpci_event_io_failure(struct pci_dev *pdev, pci_channel_state_t es,
+ struct zpci_ccdf_err *ccdf)
{
struct pci_driver *driver;
pci_dev_lock(pdev);
pdev->error_state = es;
- /**
- * While vfio-pci's error_detected callback notifies user-space QEMU
- * reacts to this by freezing the guest. In an s390 environment PCI
- * errors are rarely fatal so this is overkill. Instead in the future
- * we will inject the error event and let the guest recover the device
- * itself.
- */
- if (is_passed_through(pdev))
- goto out;
+
+ zpci_store_pci_error(pdev, ccdf);
driver = to_pci_driver(pdev->dev.driver);
if (driver && driver->err_handler && driver->err_handler->error_detected)
driver->err_handler->error_detected(pdev, pdev->error_state);
-out:
+
pci_dev_unlock(pdev);
}
@@ -330,12 +346,12 @@ static void __zpci_event_error(struct zpci_ccdf_err *ccdf)
break;
case 0x0040: /* Service Action or Error Recovery Failed */
case 0x003b:
- zpci_event_io_failure(pdev, pci_channel_io_perm_failure);
+ zpci_event_io_failure(pdev, pci_channel_io_perm_failure, ccdf);
break;
default: /* PCI function left in the error state attempt to recover */
- ers_res = zpci_event_attempt_error_recovery(pdev);
+ ers_res = zpci_event_attempt_error_recovery(pdev, ccdf);
if (ers_res != PCI_ERS_RESULT_RECOVERED)
- zpci_event_io_failure(pdev, pci_channel_io_perm_failure);
+ zpci_event_io_failure(pdev, pci_channel_io_perm_failure, ccdf);
break;
}
pci_dev_put(pdev);
diff --git a/drivers/vfio/pci/vfio_pci_zdev.c b/drivers/vfio/pci/vfio_pci_zdev.c
index 0990fdb146b7..78a28db00c6d 100644
--- a/drivers/vfio/pci/vfio_pci_zdev.c
+++ b/drivers/vfio/pci/vfio_pci_zdev.c
@@ -144,24 +144,36 @@ int vfio_pci_info_zdev_add_caps(struct vfio_pci_core_device *vdev,
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;
+ zpci_start_mediated_recovery(zdev);
+
if (!vdev->vdev.kvm)
return 0;
+ ret = -ENOENT;
if (zpci_kvm_hook.kvm_register)
- return zpci_kvm_hook.kvm_register(zdev, vdev->vdev.kvm);
+ ret = zpci_kvm_hook.kvm_register(zdev, vdev->vdev.kvm);
- return -ENOENT;
+ if (ret)
+ zpci_stop_mediated_recovery(zdev);
+
+ return ret;
}
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;
+
+ zpci_stop_mediated_recovery(zdev);
+
+ if (!vdev->vdev.kvm)
return;
if (zpci_kvm_hook.kvm_unregister)
--
2.43.0
^ permalink raw reply related [flat|nested] 10+ messages in thread* [PATCH v19 2/3] vfio-pci/zdev: Add a device feature for error information
2026-06-15 18:36 [PATCH v19 0/3] [VFIO] Error recovery for vfio-pci devices on s390x Farhan Ali
2026-06-15 18:36 ` [PATCH v19 1/3] s390/pci: Store PCI error information for passthrough devices Farhan Ali
@ 2026-06-15 18:36 ` Farhan Ali
2026-06-15 18:49 ` sashiko-bot
2026-06-23 21:07 ` Alex Williamson
2026-06-15 18:36 ` [PATCH v19 3/3] vfio/pci: Remove the pcie check for VFIO_PCI_ERR_IRQ_INDEX Farhan Ali
2026-06-23 16:19 ` [PATCH v19 0/3] [VFIO] Error recovery for vfio-pci devices on s390x Farhan Ali
3 siblings, 2 replies; 10+ messages in thread
From: Farhan Ali @ 2026-06-15 18:36 UTC (permalink / raw)
To: linux-s390, linux-kernel, linux-pci
Cc: helgaas, alex, alifm, schnelle, mjrosato
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 | 43 ++++++++++++++++++++++++++++++++
include/uapi/linux/vfio.h | 30 ++++++++++++++++++++++
6 files changed, 105 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 8934b640a095..3ad16038e005 100644
--- a/arch/s390/pci/pci_event.c
+++ b/arch/s390/pci/pci_event.c
@@ -77,6 +77,25 @@ static int zpci_store_pci_error(struct pci_dev *pdev,
return 0;
}
+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 050e7542952e..27642f10fe97 100644
--- a/drivers/vfio/pci/vfio_pci_core.c
+++ b/drivers/vfio/pci/vfio_pci_core.c
@@ -1569,6 +1569,8 @@ 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..c0d6362cc4eb 100644
--- a/drivers/vfio/pci/vfio_pci_zdev.c
+++ b/drivers/vfio/pci/vfio_pci_zdev.c
@@ -141,6 +141,49 @@ 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))) {
+ dev_warn_ratelimited(device->dev,
+ "Failed to handle PCI error event for PCI function 0x%x",
+ zdev->fid);
+ 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..83c93193b22d 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 */
+ __u64 faddr; /* failing address */
+ __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 */
+ __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
^ permalink raw reply related [flat|nested] 10+ messages in thread* Re: [PATCH v19 2/3] vfio-pci/zdev: Add a device feature for error information
2026-06-15 18:36 ` [PATCH v19 2/3] vfio-pci/zdev: Add a device feature for error information Farhan Ali
@ 2026-06-15 18:49 ` sashiko-bot
2026-06-23 21:07 ` Alex Williamson
1 sibling, 0 replies; 10+ messages in thread
From: sashiko-bot @ 2026-06-15 18:49 UTC (permalink / raw)
To: Farhan Ali
Cc: Alexander Gordeev, Vasily Gorbik, linux-s390, linux-pci,
Heiko Carstens
Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The UAPI struct `vfio_device_feature_zpci_err` uses C bitfields, which violates UAPI design principles and breaks cross-architecture/cross-compiler compatibility.
--
commit 894c3dcf471b795ab55da889778d75f212c1eee2
Author: Farhan Ali <alifm@linux.ibm.com>
vfio-pci/zdev: Add a device feature for error information
For zPCI devices, platform specific error information is provided by firmware.
This commit adds a new device feature to expose this error information to
userspace to enable recovery.
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index 5de618a3a5eee..83c93193b22de 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 */
> + __u64 faddr; /* failing address */
> + __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 */
[Severity: Medium]
Does this UAPI struct violate kernel UAPI design principles by using C
bitfields?
The C standard does not specify the memory layout of bitfields, leaving it
entirely up to the compiler and target endianness. Placing bitfields directly in
a globally exposed UAPI header could mean that generic userspace tools or
hypervisors compiled with different compilers or on architectures with different
endianness might map these fields to the wrong bits when interpreting the
struct.
Could these be replaced with a standard __u32 variable alongside explicit
#define bitmasks and shifts?
> + __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 -------- */
--
Sashiko AI review · https://sashiko.dev/#/patchset/20260615183616.2902-1-alifm@linux.ibm.com?part=2
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH v19 2/3] vfio-pci/zdev: Add a device feature for error information
2026-06-15 18:36 ` [PATCH v19 2/3] vfio-pci/zdev: Add a device feature for error information Farhan Ali
2026-06-15 18:49 ` sashiko-bot
@ 2026-06-23 21:07 ` Alex Williamson
1 sibling, 0 replies; 10+ messages in thread
From: Alex Williamson @ 2026-06-23 21:07 UTC (permalink / raw)
To: Farhan Ali
Cc: linux-s390, linux-kernel, linux-pci, helgaas, schnelle, mjrosato,
alex
On Mon, 15 Jun 2026 11:36:15 -0700
Farhan Ali <alifm@linux.ibm.com> wrote:
> 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 | 43 ++++++++++++++++++++++++++++++++
> include/uapi/linux/vfio.h | 30 ++++++++++++++++++++++
> 6 files changed, 105 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 8934b640a095..3ad16038e005 100644
> --- a/arch/s390/pci/pci_event.c
> +++ b/arch/s390/pci/pci_event.c
> @@ -77,6 +77,25 @@ static int zpci_store_pci_error(struct pci_dev *pdev,
> return 0;
> }
>
> +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 050e7542952e..27642f10fe97 100644
> --- a/drivers/vfio/pci/vfio_pci_core.c
> +++ b/drivers/vfio/pci/vfio_pci_core.c
> @@ -1569,6 +1569,8 @@ 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..c0d6362cc4eb 100644
> --- a/drivers/vfio/pci/vfio_pci_zdev.c
> +++ b/drivers/vfio/pci/vfio_pci_zdev.c
> @@ -141,6 +141,49 @@ 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))) {
> + dev_warn_ratelimited(device->dev,
> + "Failed to handle PCI error event for PCI function 0x%x",
> + zdev->fid);
> + 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..83c93193b22d 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 */
> + __u64 faddr; /* failing address */
> + __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 */
> + __u32 reserved3;
> + __u16 reserved4;
> + __u16 pec; /* PCI event code */
> + __u8 reserved5[28]; /* Allow for future expansion */
> +};
In v18 I probed whether this should be passed as opaque data as we're
doing for FMB, which was declined because the user doesn't know the
size. However, the fmb_length is provided through a device info cap,
where we could extend the existing zpci info cap with a v3 that does
report this fixed size. That doesn't seem like an insurmountable
barrier.
In the implementation here, we have the worst combination of
trade-offs, reserved fields for some vague notion of future expansion
and bitfields that mimic the architecture specification but don't fit
well into a uAPI as their position is compiler dependent.
This should either fully abandon the architecture layout and create a
well defined, naturally aligned uAPI structure, or extend the zpci info
cap to report the size and pass the error data as opaque.
As Bjorn notes, we're already into the merge window, so this is at best
v7.3 material, and as we've designed the split, merging the vfio
changes will be dependent on a branch provided with the PCI changes.
Thanks,
Alex
^ permalink raw reply [flat|nested] 10+ messages in thread
* [PATCH v19 3/3] vfio/pci: Remove the pcie check for VFIO_PCI_ERR_IRQ_INDEX
2026-06-15 18:36 [PATCH v19 0/3] [VFIO] Error recovery for vfio-pci devices on s390x Farhan Ali
2026-06-15 18:36 ` [PATCH v19 1/3] s390/pci: Store PCI error information for passthrough devices Farhan Ali
2026-06-15 18:36 ` [PATCH v19 2/3] vfio-pci/zdev: Add a device feature for error information Farhan Ali
@ 2026-06-15 18:36 ` Farhan Ali
2026-06-15 18:52 ` sashiko-bot
2026-06-23 16:19 ` [PATCH v19 0/3] [VFIO] Error recovery for vfio-pci devices on s390x Farhan Ali
3 siblings, 1 reply; 10+ messages in thread
From: Farhan Ali @ 2026-06-15 18:36 UTC (permalink / raw)
To: linux-s390, linux-kernel, linux-pci
Cc: helgaas, alex, alifm, schnelle, mjrosato, Julian Ruess
The error signaling is configured for the vast majority of devices and it's
extremely rare that it fires anyway. Removing the pcie check will allow
userspace to be notified on errors for legacy PCI devices. The Internal
Shared Memory (ISM) device on s390 is one such device. For PCI devices on
IBM s390 error recovery involves platform firmware and notification to
operating system is done by architecture specific way. So the ISM device
can still be recovered when notified of an error.
Reviewed-by: Julian Ruess <julianr@linux.ibm.com>
Reviewed-by: Niklas Schnelle <schnelle@linux.ibm.com>
Reviewed-by: Alex Williamson <alex@shazbot.org>
Signed-off-by: Farhan Ali <alifm@linux.ibm.com>
---
drivers/vfio/pci/vfio_pci_core.c | 8 ++------
drivers/vfio/pci/vfio_pci_intrs.c | 3 +--
2 files changed, 3 insertions(+), 8 deletions(-)
diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
index 27642f10fe97..cd3ce30d22f5 100644
--- a/drivers/vfio/pci/vfio_pci_core.c
+++ b/drivers/vfio/pci/vfio_pci_core.c
@@ -821,8 +821,7 @@ static int vfio_pci_get_irq_count(struct vfio_pci_core_device *vdev, int irq_typ
return (flags & PCI_MSIX_FLAGS_QSIZE) + 1;
}
} else if (irq_type == VFIO_PCI_ERR_IRQ_INDEX) {
- if (pci_is_pcie(vdev->pdev))
- return 1;
+ return 1;
} else if (irq_type == VFIO_PCI_REQ_IRQ_INDEX) {
return 1;
}
@@ -1198,11 +1197,8 @@ static int vfio_pci_ioctl_get_irq_info(struct vfio_pci_core_device *vdev,
switch (info.index) {
case VFIO_PCI_INTX_IRQ_INDEX ... VFIO_PCI_MSIX_IRQ_INDEX:
case VFIO_PCI_REQ_IRQ_INDEX:
- break;
case VFIO_PCI_ERR_IRQ_INDEX:
- if (pci_is_pcie(vdev->pdev))
- break;
- fallthrough;
+ break;
default:
return -EINVAL;
}
diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c
index 33944d4d9dc4..64f80f64ff57 100644
--- a/drivers/vfio/pci/vfio_pci_intrs.c
+++ b/drivers/vfio/pci/vfio_pci_intrs.c
@@ -859,8 +859,7 @@ int vfio_pci_set_irqs_ioctl(struct vfio_pci_core_device *vdev, uint32_t flags,
case VFIO_PCI_ERR_IRQ_INDEX:
switch (flags & VFIO_IRQ_SET_ACTION_TYPE_MASK) {
case VFIO_IRQ_SET_ACTION_TRIGGER:
- if (pci_is_pcie(vdev->pdev))
- func = vfio_pci_set_err_trigger;
+ func = vfio_pci_set_err_trigger;
break;
}
break;
--
2.43.0
^ permalink raw reply related [flat|nested] 10+ messages in thread* Re: [PATCH v19 0/3] [VFIO] Error recovery for vfio-pci devices on s390x
2026-06-15 18:36 [PATCH v19 0/3] [VFIO] Error recovery for vfio-pci devices on s390x Farhan Ali
` (2 preceding siblings ...)
2026-06-15 18:36 ` [PATCH v19 3/3] vfio/pci: Remove the pcie check for VFIO_PCI_ERR_IRQ_INDEX Farhan Ali
@ 2026-06-23 16:19 ` Farhan Ali
2026-06-23 16:33 ` Bjorn Helgaas
3 siblings, 1 reply; 10+ messages in thread
From: Farhan Ali @ 2026-06-23 16:19 UTC (permalink / raw)
To: linux-s390, linux-kernel, linux-pci; +Cc: helgaas, alex, schnelle, mjrosato
Polite ping for this series :)
Thanks
Farhan
On 6/15/2026 11:36 AM, Farhan Ali wrote:
> Hi Alex,
>
> This patch set includes only the VFIO patches of the original series for
> error recovery for vfio-pci devices on s390x [1]. Breaking up the patch
> series into PCI and VFIO only patches to make merging easier based on our
> discussion [2].
>
> Thanks
> Farhan
>
> [1] https://lore.kernel.org/all/20260520171113.1111-1-alifm@linux.ibm.com/
> [2] https://lore.kernel.org/all/20260602163344.1eda12d2@shazbot.org/
>
> ChangeLog
> ---------
> v18 https://lore.kernel.org/all/20260603182415.2324-1-alifm@linux.ibm.com/
> v18 -> v19
> - Fix hole in struct vfio_device_feature_zpci_err.
> - Remove reset_done() callback for vfio-pci driver.
> - Rebase on 7.1-rc7
>
> v17 -> v18
> - Print a warn with dev_warn_ratelimited() for copy_to_user failure.
> - Rebase on 7.1-rc6.
> - Break patch series into VFIO patch set.
>
> Farhan Ali (3):
> s390/pci: Store PCI error information for passthrough devices
> vfio-pci/zdev: Add a device feature for error information
> vfio/pci: Remove the pcie check for VFIO_PCI_ERR_IRQ_INDEX
>
> arch/s390/include/asm/pci.h | 32 +++++++
> arch/s390/pci/pci.c | 1 +
> arch/s390/pci/pci_event.c | 137 +++++++++++++++++++-----------
> drivers/vfio/pci/vfio_pci_core.c | 10 +--
> drivers/vfio/pci/vfio_pci_intrs.c | 3 +-
> drivers/vfio/pci/vfio_pci_priv.h | 9 ++
> drivers/vfio/pci/vfio_pci_zdev.c | 61 ++++++++++++-
> include/uapi/linux/vfio.h | 30 +++++++
> 8 files changed, 221 insertions(+), 62 deletions(-)
>
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH v19 0/3] [VFIO] Error recovery for vfio-pci devices on s390x
2026-06-23 16:19 ` [PATCH v19 0/3] [VFIO] Error recovery for vfio-pci devices on s390x Farhan Ali
@ 2026-06-23 16:33 ` Bjorn Helgaas
0 siblings, 0 replies; 10+ messages in thread
From: Bjorn Helgaas @ 2026-06-23 16:33 UTC (permalink / raw)
To: Farhan Ali; +Cc: linux-s390, linux-kernel, linux-pci, alex, schnelle, mjrosato
On Tue, Jun 23, 2026 at 09:19:03AM -0700, Farhan Ali wrote:
> Polite ping for this series :)
We're more than halfway through the v7.2 merge window, so it's too
late to add things for v7.2. We'll get back to this after v7.2-rc1,
i.e., next week.
> On 6/15/2026 11:36 AM, Farhan Ali wrote:
> > Hi Alex,
> >
> > This patch set includes only the VFIO patches of the original series for
> > error recovery for vfio-pci devices on s390x [1]. Breaking up the patch
> > series into PCI and VFIO only patches to make merging easier based on our
> > discussion [2].
> >
> > Thanks
> > Farhan
> >
> > [1] https://lore.kernel.org/all/20260520171113.1111-1-alifm@linux.ibm.com/
> > [2] https://lore.kernel.org/all/20260602163344.1eda12d2@shazbot.org/
> >
> > ChangeLog
> > ---------
> > v18 https://lore.kernel.org/all/20260603182415.2324-1-alifm@linux.ibm.com/
> > v18 -> v19
> > - Fix hole in struct vfio_device_feature_zpci_err.
> > - Remove reset_done() callback for vfio-pci driver.
> > - Rebase on 7.1-rc7
> >
> > v17 -> v18
> > - Print a warn with dev_warn_ratelimited() for copy_to_user failure.
> > - Rebase on 7.1-rc6.
> > - Break patch series into VFIO patch set.
> >
> > Farhan Ali (3):
> > s390/pci: Store PCI error information for passthrough devices
> > vfio-pci/zdev: Add a device feature for error information
> > vfio/pci: Remove the pcie check for VFIO_PCI_ERR_IRQ_INDEX
> >
> > arch/s390/include/asm/pci.h | 32 +++++++
> > arch/s390/pci/pci.c | 1 +
> > arch/s390/pci/pci_event.c | 137 +++++++++++++++++++-----------
> > drivers/vfio/pci/vfio_pci_core.c | 10 +--
> > drivers/vfio/pci/vfio_pci_intrs.c | 3 +-
> > drivers/vfio/pci/vfio_pci_priv.h | 9 ++
> > drivers/vfio/pci/vfio_pci_zdev.c | 61 ++++++++++++-
> > include/uapi/linux/vfio.h | 30 +++++++
> > 8 files changed, 221 insertions(+), 62 deletions(-)
> >
^ permalink raw reply [flat|nested] 10+ messages in thread