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Tue, 24 Mar 2026 23:22:07 +0000 (GMT) Message-ID: <9c675fe3-2a2e-4dea-b306-c9ef1712bec1@linux.ibm.com> Date: Tue, 24 Mar 2026 16:22:05 -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 v11 4/9] PCI: Add additional checks for flr reset To: Bjorn Helgaas Cc: linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, lukas@wunner.de, alex@shazbot.org, kbusch@kernel.org, clg@redhat.com, stable@vger.kernel.org, schnelle@linux.ibm.com, mjrosato@linux.ibm.com, Benjamin Block References: <20260324224936.GA1157694@bhelgaas> Content-Language: en-US From: Farhan Ali In-Reply-To: <20260324224936.GA1157694@bhelgaas> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: Lruv3rkZWaqSkdLFc7x6DbkkFetiXgb7 X-Authority-Analysis: v=2.4 cv=aMr9aL9m c=1 sm=1 tr=0 ts=69c31ca2 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=IkcTkHD0fZMA:10 a=Yq5XynenixoA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=C1eItPSzQBTT7hoOHSgA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzI0MDE4MCBTYWx0ZWRfX0jRG7RgQrb8W FiCTUUupN+saU5KrR5gwv0G8wiVXt59KosFrvJRez31/0hlIs9cjRv+xO4grBKrtJd+yYyK6pU3 1r38C03A2DGpoKGmar2AzCKfrXxjCPmh84/YQI9S+YI24CIdep0F9aa2ambAm7oeyAZOMPp3aqk 2oy2xCm3e1/FYVu/q2j1EpycZU4EqjXyjlJinWd4BzyBepRSIV3CoOhy+JQgf+40F8IuQeenCRC 0+bxhkLbRyrIDtmIaXWVs2TIH47oOEI1UYqAr9k2bSE8tRoCZGjwL9IxUoatGxr4PQ8fYq+jpL6 GtyTNeGmVvTo2VoIutlIj0p4Y4SgHgXMKEdExFow+tBSmfA2cBpi3vMrWREQ8si3ZoTq2Fcclf8 fOtXiaBrBNG1nKgkA366nkzeAAELoAYN/TdDFCv6XjE+r3GedbBOGHg1niD57s628lQNo7JyNjL oMAE4HBP29kU+SJ5HGQ== X-Proofpoint-GUID: Lruv3rkZWaqSkdLFc7x6DbkkFetiXgb7 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=2026-03-24_04,2026-03-24_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 lowpriorityscore=0 adultscore=0 impostorscore=0 malwarescore=0 suspectscore=0 phishscore=0 priorityscore=1501 bulkscore=0 clxscore=1015 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2603050001 definitions=main-2603240180 On 3/24/2026 3:49 PM, 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 This makes sense, will update the subject. > >> 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 will update the message :) and update the code to use the same check at patch 3 here (will move the check to a common function). Thanks Farhan > >> if (probe) >> return 0; >> >> -- >> 2.43.0 >>