NAK Re: APPLIED [OEM-5.14] Re: [PATCH 0/2][SRU][OEM-5.14/OEM-5.17] PCI: vmd: Do not disable MSI-X remapping if interrupt remapping is enabled by IOMMU

[Timo Aaltonen]

Timo Aaltonen kirjoitti 13.5.2022 klo 20.59:
> Koba Ko kirjoitti 12.5.2022 klo 11.31:
>> BugLink: https://bugs.launchpad.net/bugs/1937295
>>
>> [Impact]
>>
>> A hardware partner discovered they were unable to install Ubuntu on 
>> some servers using VROC setups. They point to this issue involving 
>> DMAR that is blocking discovery of the VROC RAID devices:
>>
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=2565e5b69c44b4e42469afea3cc5a97e74d1ed45 
>>
>>
>> `git bisect` points to this offending commit ee81ee84f873 ("PCI:
>> vmd: Disable MSI-X remapping when possible"), which disables VMD MSI
>> remapping. The IOMMU hardware blocks the compatibility format
>> interrupt request because Interrupt Remapping Enable Status (IRES) and
>> Extended Interrupt Mode Enable (EIME) are enabled. Please refer to
>> section "5.1.4 Interrupt-Remapping Hardware Operation" in Intel VT-d
>> spec.
>>
>> To fix the issue, VMD driver still enables the interrupt remapping
>> irrespective of VMD_FEAT_CAN_BYPASS_MSI_REMAP if the IOMMU subsystem
>> enables the interrupt remapping.
>>
>> [Fix]
>>
>> 2565e5b69c44 PCI: vmd: Do not disable MSI-X remapping if interrupt 
>> remapping is enabled by IOMMU
>>
>> [Test Plan]
>>
>>      1. Boot into VRoC controller in uEFI Setup and create a raid10 disk.
>>      2. Install affected Ubuntu release on the RAID10.
>>      3. The system hangs at "Partitions formatting 33%".
>>
>> [Where problems could occur]
>>
>> The fix itself is a very small change to drivers/pci/controller/vmd.c 
>> and problems should not occur. The root cause was discovered by the 
>> hardware partner's engineers, who tested and submitted it upstream 
>> where it was accepted and landed in 5.16.
>>
>> That said, I doubt this will fix 18.04.6 as it would require a respin 
>> to get the patched kernel onto the ISO. 20.04 should pick it up in ISO 
>> in 20.04.5, so there could still be the initial issue since those ISOs 
>> would be lacking the patched kernel.
>>
>> [Other Info]
>>
>> As noted, this would need to not only land in the kernel but land in 
>> the kernel in the ISO to resolve the issue in the installation 
>> process. I'll bring this back as far as Focal with the expectation 
>> that while 20.04.4 is too late, it will be present using the GA kernel 
>> in 20.04.5 later on.
>>
>> *************************************************************************
>>
>> Original Bug Summary:
>>
>> A hardware partner has been testing 18.04 subiquity images on their 
>> servers with VROC enabled and configured in a RAID 10 setup.
>>
>> In their own words:
>> Steps to reproduce:
>>
>>      1. Boot into VRoC controller in uEFI Setup and create a raid10 disk.
>>
>>      2. Install Ubuntu 18.04.5 on the RAID10.
>>
>>      3. The system hangs at "Partitions formatting 33%".
>>
>> After looking at the launchpad 
>> (https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1896578/), the 
>> fix was included in the updated kernel.
>>
>>     [Quotes from the launchpad]
>>
>>        The released kernels are:
>>
>>                Hirsute: 5.11.0-22-generic
>>                Groovy: 5.8.0-59-generic
>>                Focal: 5.4.0-77-generic
>>                Bionic: 4.15.0-147-generic
>>
>> I've asked them to also confirm this on 20.04.2, and check that 
>> 20.04.3 dailies fix the issue.
>>
>> It is at least a very reasonable hypothesis that this will also break 
>> on all current ISO installs as none of them are respun once released 
>> to include updated SRUs in the installation media. This currently 
>> affects 20.04.2 but that will be resolved shortly when 20.04.3 
>> releases as the GA and HWE kernels in that image should have the SRU 
>> that fixes this issue. However, 18.04 has no further releases, and 
>> even the 18.04.5 daily-live and daily images on cdimages.ubuntu.com 
>> are not built after 18.04.5 was released.
>>
>> Adrian Huang (1):
>>    PCI: vmd: Do not disable MSI-X remapping if interrupt remapping is
>>      enabled by IOMMU
>>
>> Koba Ko (1):
>>    UBUTNU: [Config] CONFIG_INTEL_IOMMU_DEFAULT_ON=y
>>
>>   debian.oem/config/annotations          | 2 +-
>>   debian.oem/config/config.common.ubuntu | 2 +-
>>   drivers/pci/controller/vmd.c           | 4 +++-
>>   3 files changed, 5 insertions(+), 3 deletions(-)
>>
> 
> applied to oem-5.14, and fixed the typo
> 
> 

Note that I dropped this from oem-5.14 for now, as enabling IOMMU in 
jammy caused issues like on bug 1965882 and bug 1971146 and it could do 
the same on focal as well.


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