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Tue, 2 Jun 2026 18:33:45 -0400 (EDT) Date: Tue, 2 Jun 2026 16:33:44 -0600 From: Alex Williamson To: Farhan Ali Cc: linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, helgaas@kernel.org, schnelle@linux.ibm.com, mjrosato@linux.ibm.com, alex@shazbot.org Subject: Re: [PATCH v17 5/7] vfio-pci/zdev: Add a device feature for error information Message-ID: <20260602163344.1eda12d2@shazbot.org> In-Reply-To: References: <20260520171113.1111-1-alifm@linux.ibm.com> <20260520171113.1111-6-alifm@linux.ibm.com> <20260602143202.6395e9e2@shazbot.org> X-Mailer: Claws Mail 4.4.0 (GTK 3.24.52; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Tue, 2 Jun 2026 14:38:56 -0700 Farhan Ali wrote: > On 6/2/2026 1:32 PM, Alex Williamson wrote: > > On Wed, 20 May 2026 10:11:11 -0700 > > Farhan Ali 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 > >> Reviewed-by: Niklas Schnelle > >> Signed-off-by: Farhan Ali > >> --- > >> 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 cf2ffa21ab8c..db1b44baf8fa 100644 > >> --- a/arch/s390/pci/pci_event.c > >> +++ b/arch/s390/pci/pci_event.c > >> @@ -75,6 +75,25 @@ 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..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; > >> +} > > There's a concern here that the error is dequeued but we can still fail > > resulting in a lost error. Is that a sufficiently unlikely scenario to > > ignore or should it at least be documented? > > IMHO this scenario would be unlikely and could be ignored. I think to > handle this we would need something like a peek() API and only remove > and update the pending_errs if copy_to_user succeeds. This would be > adding more complexity for a relatively low possibility of failure. Or just a dev_warn_ratelimited(). > >> + > >> 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 > >> + > > There are currently at least 4 different patch series, including this > > one, that are vying for device feature allocations. This series spans > > PCI, s390, and vfio, and I'm not entirely sure which maintainer should > > take it. With Niklas' review on patch 4, should we ask Bjorn to take > > 1-3 through PCI, share a branch, and I could merge 4-7 through vfio? > > Thanks, > > > > Alex > > If it helps I can break the series into PCI only and vfio only patches. > Please let me know if there is anything I can help with to make the > merge easier. Let's do that. Thanks, Alex