Public bug reported:
SRU Justification
[ Impact ]
* Regression testing for the 2026.10.26 cycle exposed an issue where
ARM64 instances on Azure with 64K pages enabled fail to boot. The kernel
log hangs early on during boot, indicating an early panic.
[ Fix ]
* Revert commit ffee5b49b764 ("arm64: mm: Don't remap pgtables for
allocate vs populate"). The upstream 6.6.y stable tree has actually
picked up and then reverted this commit due to the boot issue.
[ Test Plan ]
* Compile tested
* Boot-tested on ARM64 instances with 64K page size enabled on Azure (both
Ampere and Cobalt) to confirm that they don't hang anymore.
[ Where problems could occur ]
* This change will slightly worsen the boot time for 64K-enabled ARM64
instances, as its removing an optimization. Other issues here could
impact the early boot of those instances.
** Affects: linux-azure (Ubuntu)
Importance: Critical
Assignee: Vinicius Peixoto (vpeixoto)
Status: In Progress
** Affects: linux-azure (Ubuntu Noble)
Importance: Critical
Assignee: Vinicius Peixoto (vpeixoto)
Status: In Progress
** Description changed:
SRU Justification
[ Impact ]
* Regression testing for the 2026.10.26 cycle exposed an issue where
ARM64 instances on Azure with 64K pages enabled fail to boot. The kernel
log hangs early on during boot, indicating an early panic.
[ Fix ]
* Revert commit ffee5b49b764 ("arm64: mm: Don't remap pgtables for
allocate vs populate"). The upstream 6.6.y stable tree has actually
picked up and then reverted this commit due to the boot issue.
[ Test Plan ]
* Compile tested
- * Tested on ARM64 instances with 64K page size enabled on Azure (both Ampere
and Cobalt).
+ * Boot-tested on ARM64 instances with 64K page size enabled on Azure (both
Ampere and Cobalt) to confirm that they don't hang anymore.
[ Where problems could occur ]
* This change will slightly worsen the boot time for 64K-enabled ARM64
instances, as its removing an optimization. Other issues here could
impact the early boot of those instances.
** Changed in: linux-azure (Ubuntu)
Assignee: (unassigned) => Vinicius Peixoto (vpeixoto)
** Changed in: linux-azure (Ubuntu)
Importance: Undecided => Critical
** Changed in: linux-azure (Ubuntu)
Status: New => In Progress
** Also affects: linux-azure (Ubuntu Noble)
Importance: Undecided
Status: New
** Changed in: linux-azure (Ubuntu Noble)
Status: New => In Progress
** Changed in: linux-azure (Ubuntu Noble)
Importance: Undecided => Critical
** Changed in: linux-azure (Ubuntu Noble)
Assignee: (unassigned) => Vinicius Peixoto (vpeixoto)
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https://bugs.launchpad.net/bugs/2173630
Title:
64K-enabled ARM64 instances failing to boot on Azure
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