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Wed, 29 Jul 2026 20:28:46 +0000 (GMT) Received: from [9.61.253.71] (unknown [9.61.253.71]) by smtpav03.dal12v.mail.ibm.com (Postfix) with ESMTP; Wed, 29 Jul 2026 20:28:46 +0000 (GMT) Message-ID: <46fede14-a740-4d66-98b3-c840e03e8634@linux.ibm.com> Date: Wed, 29 Jul 2026 13:28:46 -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 v1] vfio/pci: Avoid mapping BARs for devices with non-mappable BARs To: Matthew Rosato , linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, kvm@vger.kernel.org Cc: borntraeger@linux.ibm.com, alex@shazbot.org, mattev@meta.com, schnelle@linux.ibm.com References: <20260729181116.1373-1-alifm@linux.ibm.com> Content-Language: en-US From: Farhan Ali In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: lOUj0GzmSEQ1dc8vP6e6KdR-Dx1lQvDa X-Proofpoint-ORIG-GUID: lOUj0GzmSEQ1dc8vP6e6KdR-Dx1lQvDa X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzI5MDE1NSBTYWx0ZWRfX5gIBPt2RmCpK p9hv2LzASoJP7aAljtccigFkYPck5m+ul+EsFUpxX00OxGR8xDQex7YgNkiiuXbMDB2dc3UU1kd K0KcKXGb3xk7/IX3VQ33t/SleorWCzd6MJUuRtvsxQNjLB7LMtorGIb6kLmT3kiYDzah4kcFCUq RQoIskjljAp2H5SN3tj26jaEnvfdmSWa8OeV/f6OdR+ztFgJbrOQCJ9DakBAvBIBRr4rKoXOrNC 5Ts1idwce9jMhQQ9UpFhSfT9KMeg7vLelPhrKxt0khlMzzEZ+6Bh87XNlVDsV2ny20/OJwcbUvm N19/69j6+N8UDsIpf+rqulUu75meVxDegm4SIjKCMM1Bnv8HsW3070CRZ6SAuLs9xWOmn/kAHmV d5i16i8poRd5eOIIMzbDmNHoHjM0KtsJ25wXvevAorDkkqMIGSparpGzGdBvt8weo2bTXbU1O1C 7Y7utuhIy8fHtfdrMdQ== X-Authority-Analysis: v=2.4 cv=SKFykuvH c=1 sm=1 tr=0 ts=6a6a6281 cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=IkcTkHD0fZMA:10 a=RAioF0-LDSMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=VnNF1IyMAAAA:8 a=v9EabsQgdZcjpZ5jZmQA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Info: AW1haW4tMjYwNzI5MDE1NSBTYWx0ZWRfX1reYxllMHmjx iMzBYiythzpY5ELjdij5w9wPEN2L9rWgoBRuQBjeYktWX8h7IVRgZjABV63ZOlWs7peeCncirfZ RJsiJ70Ismhq7wYOkpDIasJp85JZQVE= X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-07-29_07,2026-07-29_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 clxscore=1015 adultscore=0 lowpriorityscore=0 bulkscore=0 impostorscore=0 phishscore=0 spamscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607290155 On 7/29/2026 12:41 PM, Matthew Rosato wrote: > On 7/29/26 2:11 PM, Farhan Ali wrote: >> vfio_pci_core_map_bars() calls pci_iomap() to set up BAR resources, but not >> all devices support having their BARs mapped by the CPU. The >> non_mappable_bars flag indicates that a PCI device's BARs cannot be >> accessed by the CPU. The ISM device on s390 is one such device. The BAR >> size for an ISM device is 256 TiB, and attempting to map the BAR will lead >> to warnings: >> >> vmalloc_node_range for size 281474976714752 failed: Address range >> restricted to 0x2110bab00000 - 0x21903ab00000 >> >> Use pdev->non_mappable_bars to skip pci_iomap() for such devices. This flag >> is set by the PCI core at enumeration time and already serves the same >> purpose in vfio_pci_probe_mmaps(). >> >> Fixes: 05f2a68b407a ("vfio/pci: Set up BAR resources and maps in vfio_pci_core_enable()") >> Reported-by: Christian Borntraeger >> Signed-off-by: Farhan Ali >> --- >> drivers/vfio/pci/vfio_pci_core.c | 3 +++ >> 1 file changed, 3 insertions(+) >> >> diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c >> index 3f11a9624b9c..6a184588ff23 100644 >> --- a/drivers/vfio/pci/vfio_pci_core.c >> +++ b/drivers/vfio/pci/vfio_pci_core.c >> @@ -554,6 +554,9 @@ static void vfio_pci_core_map_bars(struct vfio_pci_core_device *vdev) >> >> vdev->barmap[bar] = IOMEM_ERR_PTR(-ENODEV); >> >> + if (pdev->non_mappable_bars) >> + continue; >> + > This would work for the ISM case at least, but I wonder: should we check > vdev->bar_mmap_supported[bar] instead? > > My question boils down to: do we still want messages for some of the > cases where we set vdev->bar_mmap_supported[bar] = false in > vfio_pci_probe_mmaps()? AFAIU vfio_pci_probe_mmaps() is only called in vfio_pci_core_finish_enable(). Since vfio_pci_core_map_bars() is called in vfio_pci_core_enable(), and before vfio_pci_core_finish_enable(), bar_mmap_supported would be false here for all devices. So I don't think it would work here, unless I missed something? Thanks Farhan > > Or should the messages only print when we probed, thought the bar could > be mmap'd (vdev->bar_mmap_supported[bar] == true), and now hit a failure? > > Thanks, > Matt > >> if (!pci_resource_len(pdev, i)) >> continue; >>