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Tue, 2 Jun 2026 21:38:57 +0000 (GMT) Received: from [9.61.249.141] (unknown [9.61.249.141]) by smtpav02.dal12v.mail.ibm.com (Postfix) with ESMTP; Tue, 2 Jun 2026 21:38:57 +0000 (GMT) Message-ID: Date: Tue, 2 Jun 2026 14:38:56 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v17 5/7] vfio-pci/zdev: Add a device feature for error information To: Alex Williamson 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 References: <20260520171113.1111-1-alifm@linux.ibm.com> <20260520171113.1111-6-alifm@linux.ibm.com> <20260602143202.6395e9e2@shazbot.org> Content-Language: en-US From: Farhan Ali In-Reply-To: <20260602143202.6395e9e2@shazbot.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjAyMDIxMCBTYWx0ZWRfXz8r/gaSk6aVB F+b+S2YkballFBoaVQ6COvsSzjpFhToTP0WTpqDFWv+RqGAXTDq+4vVNuWN0g/Tpb69OfdEG0iU mwz7qiYxpSPlMVQKJnQASOjfb0R10BCO4BGg/S6csm3prDstB0qIOysBCFgjG3a69Ve2QgtPLta Kg4XVi3JndFA2T1ScLbfJxse8EO1GXuvXDgTVRIrl/kNJS/CEjm6B0nEcRmPyq09Hw2EL6XDNY0 4OGysGrR3Gl1vEQMaif/cNSjMvLQHAooo2TwfdZIHsvbbrS7SlkluHGpZp4jroED6iSQ8NpFOvV NDZ7YcepT4/WdTD6Ha4VOZi1EdS92daIRrpnqOsQW/fE6AqbRjafvXNGQ2JIq3T78PkuKFpVm4U GzmzdZhZEoStR7w7nuGINHkyv3FKWNd3a7KOXc1fDBnxeKn/1yYgJKHa3MxQMEfXc7ozpHcABVU Nv+FW1Q1Z4bzt0w+bLw== X-Proofpoint-GUID: U_7TgJ7qY5rVqdiFGn4niH1FMOs95q5l X-Proofpoint-ORIG-GUID: U_7TgJ7qY5rVqdiFGn4niH1FMOs95q5l X-Authority-Analysis: v=2.4 cv=DZknbPtW c=1 sm=1 tr=0 ts=6a1f4d75 cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=IkcTkHD0fZMA:10 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=VnNF1IyMAAAA:8 a=y--LQT-nAaOemKz3C48A:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.125,FMLib:17.12.100.49 definitions=2026-06-02_04,2026-05-28_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 clxscore=1015 suspectscore=0 impostorscore=0 lowpriorityscore=0 phishscore=0 malwarescore=0 priorityscore=1501 bulkscore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605210000 definitions=main-2606020210 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. > >> + >> 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. Thanks Farhan