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Wed, 25 Mar 2026 18:40:20 +0000 (GMT) Message-ID: <2c6e8399-73df-4552-9603-218b9b42c4bc@linux.ibm.com> Date: Wed, 25 Mar 2026 11:40:20 -0700 Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v11 4/9] PCI: Add additional checks for flr reset To: Alex Williamson , Bjorn Helgaas Cc: linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, lukas@wunner.de, kbusch@kernel.org, clg@redhat.com, stable@vger.kernel.org, schnelle@linux.ibm.com, mjrosato@linux.ibm.com, Benjamin Block References: <20260316191544.2279-5-alifm@linux.ibm.com> <20260324224936.GA1157694@bhelgaas> <20260325102504.56140878@shazbot.org> Content-Language: en-US From: Farhan Ali In-Reply-To: <20260325102504.56140878@shazbot.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: PhwFkBj36F4v8uM00_tb2YPUYYejpGLK X-Proofpoint-ORIG-GUID: PhwFkBj36F4v8uM00_tb2YPUYYejpGLK X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzI1MDEzMyBTYWx0ZWRfX5TjbkQkMclNQ H2nQ98cuo8WEchIdqKtjhC6Fq4n598u3bH+LgEHs6+sn9PVTXXcWRcsvP2PA4S7NCiUoFCIds3T NRzVbp5nMwEUKOt9w4JQlNc6P5+5wDiahq3kDH/aPQdoHOSMHU3dWvwrNKlWqtPj76g833c12oj nCcD/+Z658xfzMxxlS22jl+T/fyW5JEESxM+SXmyXDSrZugA7OT3WC/+AlDlUGqGqqslTIxrVtN 2iAYXQLhdaj6Q5hYne8d8oL/niNIuBRSG2cwIwp37gSqIVD/Xp1O6/UxsRG+Txc6+/3QjIkmVZb oa5Aq8HGB7Aqj7TF3bLyEht2h6O83HILk72ea255zuXqMRERFEAq5AR+fW/iC2j9AHyLwGCadln MfQXDrCUyisFs13qD4UOqUS+BBkA8ockaNJ8mAXeQcFoLc/0BKbWi5ybkOYzAucRNWN9xr8y715 mtwp83d63F3QF3PWFuA== X-Authority-Analysis: v=2.4 cv=KbXfcAYD c=1 sm=1 tr=0 ts=69c42c17 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=RzCfie-kr_QcCd8fBx8p:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=yOeL3KzSd5q1tlI96GIA:9 a=QEXdDO2ut3YA:10 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=2026-03-25_05,2026-03-24_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 impostorscore=0 malwarescore=0 adultscore=0 clxscore=1015 priorityscore=1501 bulkscore=0 lowpriorityscore=0 phishscore=0 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2603050001 definitions=main-2603250133 On 3/25/2026 9:25 AM, Alex Williamson wrote: > On Tue, 24 Mar 2026 17:49:36 -0500 > Bjorn Helgaas wrote: > >> On Mon, Mar 16, 2026 at 12:15:39PM -0700, Farhan Ali wrote: >>> If a device is in an error state, then any reads of device registers can >>> return error value. Add additional checks to validate if a device is in an >>> error state before doing an flr reset. >> s/flr/FLR/ (also in subject) >> >> Also please extend the subject to say something specific about the >> "additional checks". E.g., >> >> PCI: Fail FLR when config space inaccessible >> >>> Cc: stable@vger.kernel.org >>> Reviewed-by: Benjamin Block >>> Reviewed-by: Niklas Schnelle >>> Signed-off-by: Farhan Ali >>> --- >>> drivers/pci/pci.c | 7 +++++++ >>> 1 file changed, 7 insertions(+) >>> >>> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c >>> index 373421f4b9d8..8e4d924f4e88 100644 >>> --- a/drivers/pci/pci.c >>> +++ b/drivers/pci/pci.c >>> @@ -4371,12 +4371,19 @@ EXPORT_SYMBOL_GPL(pcie_flr); >>> */ >>> int pcie_reset_flr(struct pci_dev *dev, bool probe) >>> { >>> + u32 reg; >>> + >>> if (dev->dev_flags & PCI_DEV_FLAGS_NO_FLR_RESET) >>> return -ENOTTY; >>> >>> if (!(dev->devcap & PCI_EXP_DEVCAP_FLR)) >>> return -ENOTTY; >>> >>> + if (pcie_capability_read_dword(dev, PCI_EXP_DEVCAP, ®)) { >>> + pci_warn(dev, "Device unable to do an FLR\n"); >>> + return -ENOTTY; >>> + } >> I guess the point of this is to detect devices that are inaccessible? >> The same sort of thing as in pci_dev_save_and_disable() from patch >> 3/9? But we use "dev->error_state == pci_channel_io_perm_failure" >> instead? >> >> No matter what we do, this has the same race as in patch 3/9. And I >> think using dev->error_state also depends on AER being enabled, which >> cuts out many PCIe devices. >> >> I think using the same exact code as in pci_dev_save_and_disable() >> would be more straightforward. And also the same sort of wording in >> the message, e.g., "Device config space inaccessible; unable to FLR" >> or similar. I foresee many of these messages in my future, and it >> will be helpful to have a specific clue about why FLR failed :) > I think pci_af_flr() and pci_pm_reset() are all subject to this as > well, some of the device specific resets too. Maybe we need a common > helper with a string provided so we can differentiate the callers, even > if we don't make all the conversions in this series. Thanks, > > Alex Yeah I was planning on implementing a common function in the next revision. Will include a string parameter to differentiate the callers. And yeah I prefer not to update pci_af_flr() or pci_pm_reset() as part of this series since I don't have the devices to test those paths. Thanks Farhan