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Tue, 29 Oct 2024 11:27:43 GMT Received: from smtpav06.dal12v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 481E858055; Tue, 29 Oct 2024 11:27:43 +0000 (GMT) Received: from smtpav06.dal12v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 4448558043; Tue, 29 Oct 2024 11:27:42 +0000 (GMT) Received: from [9.152.212.119] (unknown [9.152.212.119]) by smtpav06.dal12v.mail.ibm.com (Postfix) with ESMTP; Tue, 29 Oct 2024 11:27:42 +0000 (GMT) Message-ID: <471500804dff90f31320a2a53a48724fffe318b6.camel@linux.ibm.com> Subject: Re: [PATCHv2 2/2] pci: warn if a running device is unaware of reset From: Niklas Schnelle To: Keith Busch , linux-pci@vger.kernel.org, bhelgaas@google.com, alex.williamson@redhat.com Cc: ameynarkhede03@gmail.com, raphael.norwitz@nutanix.com, Keith Busch Date: Tue, 29 Oct 2024 12:27:41 +0100 In-Reply-To: <20241025222755.3756162-2-kbusch@meta.com> References: <20241025222755.3756162-1-kbusch@meta.com> <20241025222755.3756162-2-kbusch@meta.com> Autocrypt: addr=schnelle@linux.ibm.com; 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charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.52.4 (3.52.4-2.fc40) Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-GUID: IIyhOVLmKu2g-WB81_ZaUwlVZjOl3iHC X-Proofpoint-ORIG-GUID: 3RklWEDldDy37RFiEUK6psnmoXNF5WRT X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1051,Hydra:6.0.680,FMLib:17.12.62.30 definitions=2024-10-15_01,2024-10-11_01,2024-09-30_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 suspectscore=0 bulkscore=0 impostorscore=0 malwarescore=0 clxscore=1011 priorityscore=1501 mlxlogscore=757 lowpriorityscore=0 adultscore=0 phishscore=0 spamscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2409260000 definitions=main-2410290088 On Fri, 2024-10-25 at 15:27 -0700, Keith Busch wrote: > From: Keith Busch >=20 > If a reset is issued to a running device with a driver that didn't > register the notification callbacks, the driver may be unaware of this > event and have an inconsistent view of the device's state. Log a warning > of this event because there's nothing else indicating the event occured, > which could be confusing when debugging such situations. >=20 > Signed-off-by: Keith Busch > --- > drivers/pci/pci.c | 4 ++++ > 1 file changed, 4 insertions(+) >=20 > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c > index 338dfcd983f1e..bbf12d4998269 100644 > --- a/drivers/pci/pci.c > +++ b/drivers/pci/pci.c > @@ -5158,6 +5158,8 @@ static void pci_dev_save_and_disable(struct pci_dev= *dev) > */ > if (err_handler && err_handler->reset_prepare) > err_handler->reset_prepare(dev); > + else if (dev->driver) > + pci_warn(dev, "resetting"); > =20 > /* > * Wake-up device prior to save. PM registers default to D0 after > @@ -5191,6 +5193,8 @@ static void pci_dev_restore(struct pci_dev *dev) > */ > if (err_handler && err_handler->reset_done) > err_handler->reset_done(dev); > + else if (dev->driver) > + pci_warn(dev, "reset done"); > } > =20 > /* dev->reset_methods[] is a 0-terminated list of indices into this arra= y */ For what it's worth on s390 I think the previous proposal of having the attribute on the pci_bus would have been better in principle. On s390 the PCI bus probing is done by firmware and Linux doesn't see a pci_dev for bridges but we do create struct pci_bus for example for a PF and its child VFs. Then again we can't really do a reset on this level, other than manually going through the PCI functions and resetting them one by one. In fact we may see PCI functions on their own bus while another Linux instance (LPAR) sees other functions from that bus. So yeah, I guess it's fair not to have this attribute but still wanted to offer these thoughts. Thanks, Niklas