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Mon, 22 Jun 2026 20:22:14 +0000 (GMT) Received: from [9.61.251.231] (unknown [9.61.251.231]) by smtpav05.dal12v.mail.ibm.com (Postfix) with ESMTP; Mon, 22 Jun 2026 20:22:14 +0000 (GMT) Message-ID: <5761d5ab-abaf-468c-a931-73c16bdfc7f3@linux.ibm.com> Date: Mon, 22 Jun 2026 13:22:14 -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 , 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> <8e0cdec1d92eaadaf0739c7175e2bb78783d4524.camel@linux.ibm.com> Content-Language: en-US From: Farhan Ali In-Reply-To: <8e0cdec1d92eaadaf0739c7175e2bb78783d4524.camel@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjIyMDE5NyBTYWx0ZWRfX9BZH4xkFH+Jc hsevkW8HmnMkZiMbq/rBOkPtOTtKg3JpHYfFivG63M24X7d4AgDm3BOwhnYIl7CJd5/F9rIELbM dsHKRSlU7Xq15NFiAFKG3qg/S4BZ6DFNNVtNy1jkcOqdwquVjVIoJdMP75FRaGexZvDifOtSHfG VTTgFknq7isYxFKh4LsEuBz+2u87anucf5P5t5lkCWpXs8HFXttmTD7RSDrIfKNbY0szgB592nW rG+P2y59jz9q7guGWZvGkGJs7zxNGy/BM0XP0jyC36TGHJUa6QLtLgkhEnjW+LbuNM4zxAGv+ro UQP358OWXbdApTuutfAcOGjfCUcPFbloWinsvYDQoiyD7HMwxBOdXV0L5IL6lGKQXq31JseMrAf ddwxpyyfUYCTC/pajBe5EQDVE2skkJ/Ajj0Y9gUkhqDQhJRTb/Yyq26TbuqTtPg7hHJ2Jr7bSKq updwTFva0hYCUaGm6WA== X-Proofpoint-GUID: XID1W1wuUY-veoNt-_R3fMH6t6zdl6Z2 X-Proofpoint-Spam-Info: AW1haW4tMjYwNjIyMDE5NyBTYWx0ZWRfX8MkXHHD9E2+S Bz1/b3EJ4q8ZsxRm4AYqMryBEnoGAMwEKvF9mJAM3vk110Uk446aesAO+99xa8jWPE0ZbFECKDd bgaf+ajWBAl0FNTBnff+6oHJffbxSvY= X-Authority-Analysis: v=2.4 cv=I/lVgtgg c=1 sm=1 tr=0 ts=6a399979 cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=IkcTkHD0fZMA:10 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=VnNF1IyMAAAA:8 a=41MKBYwao-ZyPmYOq8wA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-ORIG-GUID: XID1W1wuUY-veoNt-_R3fMH6t6zdl6Z2 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=2026-06-22_04,2026-06-22_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 spamscore=0 phishscore=0 clxscore=1015 priorityscore=1501 adultscore=0 impostorscore=0 bulkscore=0 suspectscore=0 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2606220197 On 6/22/2026 11:54 AM, Niklas Schnelle wrote: > On Mon, 2026-06-22 at 10:18 -0700, 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 > SpellingL "it's" > >> restored state of device may not have the Memory bit enabled, even if a > Missing "a" in "of a device" Ah I missed correcting these. > >> 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. > The official spec term is "Memory Space Enable" and I think "can lead > to" is actually underselling it, as the PCIe spec says that accesses > are "caused to be handled as Unsupported Requests". Also as I > understand you did see this in practice. Maybe we even want a Fixes > tag? This behavior has been present since 41017f0cac92 ("[PATCH] PCI: MSI(X) save/restore for suspend/resume"), so I am not sure a fixes tag makes sense? >> Signed-off-by: Farhan Ali >> --- >> drivers/pci/msi/msi.c | 4 ++++ >> 1 file changed, 4 insertions(+) >> >> diff --git a/drivers/pci/msi/msi.c b/drivers/pci/msi/msi.c >> index 81d24a270a79..46a0d9f68a57 100644 >> --- a/drivers/pci/msi/msi.c >> +++ b/drivers/pci/msi/msi.c >> @@ -874,6 +874,7 @@ void __pci_restore_msix_state(struct pci_dev *dev) >> { >> struct msi_desc *entry; >> bool write_msg; >> + u16 cmd; >> >> if (!dev->msix_enabled) >> return; >> @@ -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); >> >> write_msg = arch_restore_msi_irqs(dev); >> >> @@ -893,6 +896,7 @@ void __pci_restore_msix_state(struct pci_dev *dev) >> } >> } >> >> + pci_write_config_word(dev, PCI_COMMAND, cmd); >> pci_msix_clear_and_set_ctrl(dev, PCI_MSIX_FLAGS_MASKALL, 0); >> } >> > Code wise this all looks good to me so feel free to add. > > Reviewed-by: Niklas Schnelle > > Thanks, > Niklas Thanks for reviewing! Thanks Farhan