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Mon, 22 Jun 2026 20:49:06 +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 20:49:06 +0000 (GMT) Message-ID: Date: Mon, 22 Jun 2026 13:49:06 -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: Thomas Gleixner , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org Cc: helgaas@kernel.org, alex@shazbot.org, schnelle@linux.ibm.com, mjrosato@linux.ibm.com References: <20260622171840.1618-1-alifm@linux.ibm.com> <20260622171840.1618-5-alifm@linux.ibm.com> <87ik7al3of.ffs@fw13> Content-Language: en-US From: Farhan Ali In-Reply-To: <87ik7al3of.ffs@fw13> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=X4Ni7mTe c=1 sm=1 tr=0 ts=6a399fc6 cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=IkcTkHD0fZMA:10 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=VnNF1IyMAAAA:8 a=VwQbUJbxAAAA:8 a=I6BqXQysMxH1PwLeqfwA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Info: AW1haW4tMjYwNjIyMDIwMSBTYWx0ZWRfX9/OaY6gjeOmW 3sfThE46CAUmVmfc6bZHvi2PvEsIxagk/IP77obw/nE/QiF79xoTprIBBBcoU3g2UJYhWj0EJ8/ MNr3u85b2SzQCsSQRYhNjI4j+rIaE2k= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjIyMDIwMSBTYWx0ZWRfX9bbhC4mjbZ8D NfOBiXDa6/l5+ibRlhY7r3Ci75bAW5DMyVNPpAaBrDGfprEGHgrqYo+uyyfoxgyuw3RYBrT9/yE 1Egr1iQFaImXE0EhVPJI0Rfkh4fPzpqjdgTtTBL3ND0VRG39XjctnrH8ww6vbko74N+HIvYBpiq GxOw2/IM2VG+RJ5p+YNRRstSq/gG0MQYHgxIZvUX5BfBqdiupWOuzl0TDsNuOrsE+1Nx4Dj7Lbg fXTVdYOZKdB3PMEXcSd8E8/zwQCJCUyivZvTpB/S3sdDICLU2A7Qse1gk8WLVziFEFWLDYBjm3T bA8sIyp3W9qdOYOHm+UP+5utQh9ab3pn87M5iz9ul1zu6Z9oH/XVBcC3s0OCtp3aVigrwGofZea 5OdSGQ9yzq5jp1QZRuOdrwhNr2E1YOd3d1oH1l2tta5qdR9fR/ocEFP/cHQRJDYBOnCnYT0242P I8WN48tPUiwPVqIc12w== X-Proofpoint-ORIG-GUID: Kd6CNkq9T2U5Ngh9O9AbzR5MSEOjooDL X-Proofpoint-GUID: Kd6CNkq9T2U5Ngh9O9AbzR5MSEOjooDL 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 phishscore=0 bulkscore=0 suspectscore=0 spamscore=0 priorityscore=1501 impostorscore=0 malwarescore=0 clxscore=1011 adultscore=0 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2606220201 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 >> --- >> 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); > 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" 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? Thanks Farhan