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Mon, 25 Aug 2025 22:28:08 +0000 (GMT) Message-ID: <042deeb6-864d-4f66-9031-4a4ba3214c94@linux.ibm.com> Date: Mon, 25 Aug 2025 15:28:08 -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 v2 2/9] PCI: Add additional checks for flr and pm reset To: Alex Williamson Cc: linux-s390@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, helgaas@kernel.org, schnelle@linux.ibm.com, mjrosato@linux.ibm.com References: <20250825171226.1602-1-alifm@linux.ibm.com> <20250825171226.1602-3-alifm@linux.ibm.com> <20250825155420.2ace4847.alex.williamson@redhat.com> Content-Language: en-US From: Farhan Ali In-Reply-To: <20250825155420.2ace4847.alex.williamson@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwODIzMDAyMSBTYWx0ZWRfX3YeFTJVTF32e 5I5kHwgcC5/DeuTqE5KPvrvmp4qFxhd5cp3ZEVdqraLCslxFyfbENZMbgXUoVdXtEC+1N+s+owK KeMwmJTiTtaggCBUAKdSRinllT49TcSDN+gnZEj7oLD5PopKmw+6dSuSK7UEvq9MB3KNVsg3xZn tqOvDoeXkRFOq3J2Kn6NyKcGuF3Jz8osZ2vDM5ixJbcfmitXIRMBsRqyugEjut/RUPfqdgWMm7R yEBI2AFD1aVPIeTcdzMtrI3HZ+wN+G72jxZ2LYqeEOFR9oea3b83Dl6KzJ17pI6dz7ZCzgstJun 167Bg8EXcgHt4mpSi5moFSCue+2+GnKjqCuVgjQ8B9F7Wb9Q6x+OCLWS1bmupMbvRbI+q+nIekV xym560Wq X-Proofpoint-ORIG-GUID: L8AFYC6BMBp_9s5H0IZqkQdYk7J4m2TH X-Proofpoint-GUID: L8AFYC6BMBp_9s5H0IZqkQdYk7J4m2TH X-Authority-Analysis: v=2.4 cv=Ndbm13D4 c=1 sm=1 tr=0 ts=68ace37b cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=IkcTkHD0fZMA:10 a=2OwXVqhp2XgA:10 a=P-IC7800AAAA:8 a=VnNF1IyMAAAA:8 a=foT7BmcOsW2tIiZqzTwA:9 a=QEXdDO2ut3YA:10 a=d3PnA9EDa4IxuAV0gXij:22 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-08-25_10,2025-08-20_03,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 impostorscore=0 clxscore=1015 phishscore=0 malwarescore=0 suspectscore=0 bulkscore=0 spamscore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2507300000 definitions=main-2508230021 On 8/25/2025 2:54 PM, Alex Williamson wrote: > On Mon, 25 Aug 2025 10:12:19 -0700 > Farhan Ali wrote: > >> If a device is in an error state, then any reads of device registers can >> return error value. Add addtional checks to validate if a device is in an >> error state before doing an flr or pm reset. > I think the thing we see in practice for a device that's wedged and > returning -1 from config space is that the FLR will timeout waiting for > a pending transaction. So this should fix that, but should we log > something? I guess it makes sense to add a warn log. > > I'm assuming AF FLR is not needed here because we don't cache the > offset and therefore won't find the capability when we search the chain > for it. Yes, based on my understanding of the when we search for the capability offset, we would return 0 if the config space read returns a -1 (https://elixir.bootlin.com/linux/v6.16.3/source/drivers/pci/pci.c#L441). > >> 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 0dd95d782022..a07bdb287cf3 100644 >> --- a/drivers/pci/pci.c >> +++ b/drivers/pci/pci.c >> @@ -4560,12 +4560,17 @@ 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, ®)) >> + return -ENOTTY; >> + >> if (probe) >> return 0; >> >> @@ -4640,6 +4645,8 @@ static int pci_pm_reset(struct pci_dev *dev, bool probe) >> return -ENOTTY; >> >> pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &csr); >> + if (PCI_POSSIBLE_ERROR(csr)) >> + return -ENOTTY; > Doesn't this turn out to be redundant to the test below? Yup, I guess i was being extra cautious. Will remove the check. Thanks Farhan >> if (csr & PCI_PM_CTRL_NO_SOFT_RESET) >> return -ENOTTY; >> > Thanks, > Alex >