** Changed in: linux-aws (Ubuntu Xenial)
Status: In Progress => Fix Committed
** Changed in: linux-aws (Ubuntu Bionic)
Status: In Progress => Fix Committed
** Changed in: linux-aws (Ubuntu Focal)
Status: In Progress => Fix Committed
** Changed in: linux-aws (Ubuntu Groovy)
Status: In Progress => Fix Committed
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https://bugs.launchpad.net/bugs/1913739
Title:
aws: properly support instance types with > 255 cpu cores
Status in linux-aws package in Ubuntu:
New
Status in linux-aws source package in Xenial:
Fix Committed
Status in linux-aws source package in Bionic:
Fix Committed
Status in linux-aws source package in Focal:
Fix Committed
Status in linux-aws source package in Groovy:
Fix Committed
Bug description:
[Impact]
To properly support instance types in AWS with > 255 cores we need to
make sure that commit c40aaaac1018ff1382f2d35df5129a6bcea3df6b
("iommu/vt-d: Gracefully handle DMAR units with no supported address
widths") is applied across all our linux-aws kernels.
[Test Case]
Tests performed by AWS.
[Fix]
Apply/backport commit c40aaaac1018ff1382f2d35df5129a6bcea3df6b.
For groovy it's a clean cherry pick.
For Focal/Bionic the backport activity is to simply rename the patched
file.
Only Xenial requires a little more backporting activity, in particular
we need to change the condition in free_iommu() checking if
iommu->iommu_dev is defined (instead of checking for iommu->iommu.ops,
that is not available in the 4.4 kernel).
[Regression potential]
This change allows to use DMAR units that were not used before (for
interrupt remapping). Theoretically this should provide a performance
improvement, but we should keep an eye about potential performance
regressions of drivers that are using IOMMU, in case they're using
this new behavior incorrectly.
Moreover, the Xenial backport required an adjustment in free_iommu()
to check when we need to call iommu_device_destroy(), if the
adjustment is not 100% correct we could introduce a potential memory
leak.
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