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Mon, 15 Sep 2025 15:43:57 GMT Received: from smtpav01.dal12v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 93EF658057; Mon, 15 Sep 2025 15:43:56 +0000 (GMT) Received: from smtpav01.dal12v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 830A358059; Mon, 15 Sep 2025 15:43:54 +0000 (GMT) Received: from [9.111.35.47] (unknown [9.111.35.47]) by smtpav01.dal12v.mail.ibm.com (Postfix) with ESMTP; Mon, 15 Sep 2025 15:43:54 +0000 (GMT) Message-ID: <3f57e4d2d317fecf50e1b87e5cce8a848e4098b3.camel@linux.ibm.com> Subject: Re: [PATCH v2 3/4] Documentation: PCI: Amend error recovery doc with DPC/AER specifics From: Niklas Schnelle To: Lukas Wunner , Bjorn Helgaas , Jonathan Corbet Cc: Terry Bowman , Ilpo Jarvinen , Sathyanarayanan Kuppuswamy , Linas Vepstas , Mahesh J Salgaonkar , Oliver OHalloran , linuxppc-dev@lists.ozlabs.org, linux-pci@vger.kernel.org, linux-doc@vger.kernel.org, Brian Norris Date: Mon, 15 Sep 2025 17:43:53 +0200 In-Reply-To: <61d8eeadb20ee71c3a852f44c863bfe0209c454d.1757942121.git.lukas@wunner.de> References: <61d8eeadb20ee71c3a852f44c863bfe0209c454d.1757942121.git.lukas@wunner.de> Autocrypt: addr=schnelle@linux.ibm.com; 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charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.56.2 (3.56.2-2.fc42) Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=BKWzrEQG c=1 sm=1 tr=0 ts=68c8343f cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=IkcTkHD0fZMA:10 a=yJojWOMRYYMA:10 a=cm27Pg_UAAAA:8 a=VnNF1IyMAAAA:8 a=KkUFHGsvljIy0fMCjwwA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: rp1qdtcWLgxhpcmnYCfvK4Aa6T-YEw2H X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwOTE1MDA4NiBTYWx0ZWRfX1cqd++TuCWYQ m5+t1oC9I5qw6bQkKIAsXLRxFjzKapNV8Z9YDoBOqopHpwqAmdnSQVuBaRc1CigaofI6jd0fsdK WGbz/njz2gzUCVxj2nabXQ4Wm6BdTOPOMovrYq6MGNAaVqHcQifpbnCqwUEl/a200inie/eSlLH zajmQCYNuct1L2VmkixfnvpWRCdck5hG7PLSZ+adAahZsv3+bxcOkNZ1OLUTsLanoWqZ+o7KING DFQ1he7uYIWzlRFTWKBRiObwPM+Igvu1zibI+nq5xZq9V/1hh3gh5YgKYBMtYQ8xn7WcS8IlXOR bMz8wbyfqOw8Q293Cd0Dby04xedV0xqnoymqbv58ihTmwXTUcqPrwfqYOkh2umsuIUCgiSdADO0 mFml4txG X-Proofpoint-ORIG-GUID: l2W4QL8GpnSeA78T2gYWmupK6pSVcEXD X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1117,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-09-15_06,2025-09-12_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 clxscore=1015 malwarescore=0 priorityscore=1501 adultscore=0 suspectscore=0 impostorscore=0 bulkscore=0 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2507300000 definitions=main-2509150086 On Mon, 2025-09-15 at 15:50 +0200, Lukas Wunner wrote: > Amend the documentation on PCI error recovery with specifics about > Downstream Port Containment and Advanced Error Reporting: >=20 > * Explain that with DPC, devices are inaccessible upon an error (similar > to EEH on powerpc) and do not become accessible until the link is > re-enabled. >=20 > * Explain that with AER, although devices may already be accessible in th= e > ->error_detected() callback, accesses should be deferred to the > ->mmio_enabled() callback for compatibility with EEH on powerpc and wit= h > s390. >=20 > Signed-off-by: Lukas Wunner > Reviewed-by: Brian Norris > --- > Documentation/PCI/pci-error-recovery.rst | 22 ++++++++++++++++++++++ > 1 file changed, 22 insertions(+) >=20 > diff --git a/Documentation/PCI/pci-error-recovery.rst b/Documentation/PCI= /pci-error-recovery.rst > index d5c661baa87f..9e1e2f2a13fa 100644 > --- a/Documentation/PCI/pci-error-recovery.rst > +++ b/Documentation/PCI/pci-error-recovery.rst > @@ -122,6 +122,10 @@ A PCI bus error is detected by the PCI hardware. On= powerpc, the slot > is isolated, in that all I/O is blocked: all reads return 0xffffffff, > all writes are ignored. > =20 > +Similarly, on platforms supporting Downstream Port Containment > +(PCIe r7.0 sec 6.2.11), the link to the sub-hierarchy with the > +faulting device is disabled. Any device in the sub-hierarchy > +becomes inaccessible. > =20 > STEP 1: Notification > -------------------- > @@ -204,6 +208,24 @@ link reset was performed by the HW. If the platform = can't just re-enable IOs > without a slot reset or a link reset, it will not call this callback, an= d > instead will have gone directly to STEP 3 (Link Reset) or STEP 4 (Slot R= eset) > =20 > +.. note:: > + > + On platforms supporting Advanced Error Reporting (PCIe r7.0 sec 6.2), > + the faulting device may already be accessible in STEP 1 (Notification= ). > + Drivers should nevertheless defer accesses to STEP 2 (MMIO Enabled) > + to be compatible with EEH on powerpc and with s390 (where devices are > + inaccessible until STEP 2). > + > + On platforms supporting Downstream Port Containment, the link to the > + sub-hierarchy with the faulting device is re-enabled in STEP 3 (Link > + Reset). Hence devices in the sub-hierarchy are inaccessible until > + STEP 4 (Slot Reset). > + > + For errors such as Surprise Down (PCIe r7.0 sec 6.2.7), the device > + may not even be accessible in STEP 4 (Slot Reset). Drivers can detect > + accessibility by checking whether reads from the device return all 1'= s > + (PCI_POSSIBLE_ERROR()). > + > .. note:: > =20 > The following is proposed; no platform implements this yet: Thanks for improving this. Makes sense to mention and spell this out explicitly. Reviewed-by: Niklas Schnelle