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Tue, 31 Mar 2026 19:27:07 +0000 (GMT) Message-ID: Date: Tue, 31 Mar 2026 12:27:05 -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 v12 5/7] vfio-pci/zdev: Add a device feature for error information To: Matthew Rosato , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org Cc: helgaas@kernel.org, lukas@wunner.de, alex@shazbot.org, clg@redhat.com, kbusch@kernel.org, schnelle@linux.ibm.com References: <20260330174011.1161-1-alifm@linux.ibm.com> <20260330174011.1161-6-alifm@linux.ibm.com> Content-Language: en-US From: Farhan Ali In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: fDZwEfLvCt8nKTNPOcG1m12O4rC-UxTx X-Authority-Analysis: v=2.4 cv=frzRpV4f c=1 sm=1 tr=0 ts=69cc200f cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=IkcTkHD0fZMA:10 a=Yq5XynenixoA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=VnNF1IyMAAAA:8 a=qNG8fd7tPmr0NF9BgyQA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-ORIG-GUID: fDZwEfLvCt8nKTNPOcG1m12O4rC-UxTx X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzMxMDE4NiBTYWx0ZWRfX2WsdkQnsqtN0 sUa7h8WWlyQsyrhPX+9luEvj2tdHIYL7cu8b9fFKA8bpsOEk3mBTTwgLeWxrFwr4hOp5VAI0RYK N1Fa8e9kATr3dHzszhms7nu7MCjQVUdZISTfIoQCDwNPsKz67EXeEDYyTTrN1Wjmn6+YaaIvLyd 8TM7st6F0pTQ1hk8ztBP5PWkNMJft62RZWexlHuadbE/gw1jZ0KNfZ2s9Ig/tlVBFJiXK941Tju U6sSZGa0xdbYdXdagIH+mWJAv2QKBReun7Zjp7W7rYv8WYskf/qQXlWd/AfzneX+dkp0Lv0+ZQr FsJeK4L4rSbkG5pyrfnhgXO+dCVouk6sP+7wVzVEr8lu+JzwFF+H2g+70c0EiK+uG9MrDi0KV6I ivFfoAlQ0L547k0xVz8UCa8U+0gQuS2WHhRZ7WdS7nCoUiLfHbG6KcjA+mAsqqXKu905vjLr+kd irRpTtc5g2+UrWQY06A== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-03-31_04,2026-03-31_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 spamscore=0 priorityscore=1501 malwarescore=0 clxscore=1015 lowpriorityscore=0 bulkscore=0 adultscore=0 suspectscore=0 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2603050001 definitions=main-2603310186 On 3/31/2026 10:42 AM, Matthew Rosato wrote: > On 3/30/26 1:40 PM, 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. >> >> Signed-off-by: Farhan Ali > Reviewed-by: Matthew Rosato > > Nits and a questions below > > >> +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_dev *zdev; >> + int head = 0; >> + 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; >> + >> + mutex_lock(&zdev->pending_errs_lock); >> + if (zdev->pending_errs.count) { >> + head = zdev->pending_errs.head % ZPCI_ERR_PENDING_MAX; >> + err.pec = zdev->pending_errs.err[head].pec; >> + zdev->pending_errs.head++; >> + zdev->pending_errs.count--; >> + err.pending_errors = zdev->pending_errs.count; >> + } >> + mutex_unlock(&zdev->pending_errs_lock); >> + > Question: intentionally dropping so we don't hold over the copy_to_user? > That makes sense to me; but if not then may as well use guard(mutex) > here too. Does not affect my review tag. Yes, exactly. I didn't see a need to hold the lock over copy_to_user(). Thanks Farhan > >> + err.version = 1; >> + if (copy_to_user(arg, &err, sizeof(err))) >> + 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 bb7b89330d35..2552eef42000 100644 >> --- a/include/uapi/linux/vfio.h >> +++ b/include/uapi/linux/vfio.h >> @@ -1510,6 +1510,24 @@ struct vfio_device_feature_dma_buf { >> struct vfio_region_dma_range dma_ranges[] __counted_by(nr_ranges); >> }; >> >> +/** >> + * VFIO_DEVICE_FEATURE_ZPCI_ERROR feature provides PCI error information to >> + * userspace for vfio-pci devices on s390x. On s390x PCI error recovery > 'On s390x, PCI error...' (suggest comma) > >> + * involves platform firmware and notification to operating system is done >> + * by architecture specific mechanism. Exposing this information to >> + * userspace allows userspace to take appropriate actions to handle an > 'userspace allows it to take...' (reduce repetition of the word userspace) > >> + * error on the device. The pending_errors provide any additional errors >> + * pending for the device, and userspace should read until zero. >> + */ >> + >> +struct vfio_device_feature_zpci_err { >> + __u8 version; >> + __u8 pending_errors; >> + __u16 pec; >> +}; >> + >> +#define VFIO_DEVICE_FEATURE_ZPCI_ERROR 12 >> + >> /* -------- API for Type1 VFIO IOMMU -------- */ >> >> /**