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Tue, 23 Jun 2026 16:36:41 +0000 (GMT) Received: from [9.61.246.142] (unknown [9.61.246.142]) by smtpav01.wdc07v.mail.ibm.com (Postfix) with ESMTP; Tue, 23 Jun 2026 16:36:41 +0000 (GMT) Message-ID: <730608ca-4a3f-4dd2-ab3e-4b83716a97d1@linux.ibm.com> Date: Tue, 23 Jun 2026 09:36:39 -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 v20 4/4] PCI/MSI: Enable memory decoding before restoring MSI-X messages To: Niklas Schnelle , Thomas Gleixner , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org Cc: helgaas@kernel.org, alex@shazbot.org, mjrosato@linux.ibm.com References: <20260622171840.1618-1-alifm@linux.ibm.com> <20260622171840.1618-5-alifm@linux.ibm.com> <87ik7al3of.ffs@fw13> <087b5cafd04d2fee89f3a4a941d425e967d1ee72.camel@linux.ibm.com> Content-Language: en-US From: Farhan Ali In-Reply-To: <087b5cafd04d2fee89f3a4a941d425e967d1ee72.camel@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: s7Ydh_UkrSmtD3P7B4QXaLlLVwFQjkWv X-Proofpoint-Spam-Info: AW1haW4tMjYwNjIzMDEzNCBTYWx0ZWRfX+CFI+Ad4r31W xcMUTRcz6LdevM+BGkPvAARj2UiEg3OUriQCT/hktF0nyZluhdfzUqVn7+/rp9+5TONpSLvPNBw 4k6LaLW+ElaBFtk09d+ZqTTfQzfhrOE= X-Authority-Analysis: v=2.4 cv=c62bhx9l c=1 sm=1 tr=0 ts=6a3ab61c cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=IkcTkHD0fZMA:10 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=V8glGbnc2Ofi9Qvn3v5h:22 a=VnNF1IyMAAAA:8 a=VwQbUJbxAAAA:8 a=ylRXk-n9h8MM0u5Yn-8A:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjIzMDEzNCBTYWx0ZWRfX8/MARbqvKpRs 2x0gYGPMBZCHRaOOM/otDYciPNg7YMHekSf7xTlolqXz9XO3svsNj9CYOyDjXiyv/Ko5pmNCCUo tZZwnijKoYtfSQWfa6oEysiSDqA47J4yrHSS7BJF0SxmIzz01OR8XE0DFhruVpp5nEABA8GjvA1 EmEdF9bf4WfzlwmXk07UMXb9VjsCoQBlCNTCXkUOe3pphPOiGJI8v94Y5jewbSULbJxxQwz4xaN OsPeuJJhy8SI0Z7zJk5fzApYS8dw4wkakzkOfZlCnFwSyYqjDRO6frP9GsWIsYroxKrvzoC6YCJ 6y6H6XYqpZik4LneyFkXj43SxOrDgj+rQ1TQEaG4hDBLIeK1R1OW9YQITDU5Y+GIpliJTzfW2j7 YYoWP0U5VXZ0uyGgh1vU1WizjFNKII/IWVfTuqOM35VF3D1q/lO4M4uOS1uKzXSWAweLqVSbUAk iKOiNn0pCOshuCHH3uw== X-Proofpoint-ORIG-GUID: s7Ydh_UkrSmtD3P7B4QXaLlLVwFQjkWv X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.125,FMLib:17.12.100.49 definitions=2026-06-23_03,2026-06-23_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 impostorscore=0 adultscore=0 clxscore=1015 suspectscore=0 priorityscore=1501 phishscore=0 spamscore=0 bulkscore=0 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2606230134 On 6/23/2026 4:28 AM, Niklas Schnelle wrote: > On Mon, 2026-06-22 at 13:49 -0700, Farhan Ali wrote: >> On 6/22/2026 1:29 PM, Thomas Gleixner wrote: >>> On Mon, Jun 22 2026 at 10:18, Farhan Ali wrote: >>>> The current MSI-X restoration path assumes the Command register Memory bit >>>> is enabled when writing MSI-X messages. But its possible the last saved and >>>> restored state of device may not have the Memory bit enabled, even if a >>>> device driver later enables Memory bit and MSI-X. Attempting to access >>>> Memory space without Memory bit enabled can lead to Unsupported Request >>>> (UR) from the device. Fix this by enabling Memory bit and restore >>>> it afterwards. >>>> >>>> Signed-off-by: Farhan Ali >>>> --- >>>> > --- 8< --- >>>> @@ -882,6 +883,8 @@ void __pci_restore_msix_state(struct pci_dev *dev) >>>> pci_intx_for_msi(dev, 0); >>>> pci_msix_clear_and_set_ctrl(dev, 0, >>>> PCI_MSIX_FLAGS_ENABLE | PCI_MSIX_FLAGS_MASKALL); >>>> + pci_read_config_word(dev, PCI_COMMAND, &cmd); >>>> + pci_write_config_word(dev, PCI_COMMAND, cmd | PCI_COMMAND_MEMORY); >>> Can we please have a comment there which explains this? Three month down >>> the road this will results in head scratching otherwise. >>> >>> I agree with Niklas that this wants a Fixes and a Cc:stable tag. >>> >>> Other than that: >>> >>> Reviewed-by: Thomas Gleixner >>> >>> Thanks, >>> >>> tglx >>> >> I can add a comment, how about something like below? >> >> "The restored device state may not have Memory decoding enabled in >> Command register. Since the MSI-X was enabled for the device, enable >> Memory decoding before restoring MSI-X" > Missing "the" before "Command register" other than that this sounds > good to me and I agree with Thomas that a comment makes sense here. > >> For the Fixes tag, do you have a suggestion for a commit? This behavior >> has been present since 41017f0cac92 ("[PATCH] PCI: MSI(X) save/restore >> for suspend/resume" which introduced these restore functions. So should >> be Fixes against 41017f0cac92? > I'm not sure but my guess would be that for suspend/resume this isn't > an issue since the suspend part would save the state with Memory Space > enabled. So it wouldn't be broken in this original use-case. I think > the problem only occurs in case restore is done for error recovery. > Might it make sense to have the Fixes tag point to a2f1e22390ac > ("PCI/ERR: Ensure error recoverability at all times") even though that > only helps to expose the issue? > > Thanks, > Niklas Yeah, commit a2f1e22390ac ("PCI/ERR: Ensure error recoverability at all times") exposes this issue. I am okay if we want Fixes tag to point to this change, unless someone objects. I will also add a note in the commit message to specify a2f1e22390ac exposes this issue. Thanks Farhan