[SRU][P:linux][PATCH 0/1 v2] deadlock on cpu_hotplug_lock in __accept_page()

[Thibault Ferrante]

BugLink: https://bugs.launchpad.net/bugs/2109543

[ Impact ]

 * Boot hangs because of deadlock caused by mm (memory management)
   during CPU bring-up.

[ Fix ]

 * Upstream commit :
   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=4067196a52278156d18d8d6fa7f43970611b1b49

[ Test Plan ]

 * This deadlock has been uncovered in the context of confidential VMs work (AMD SNP & TDX)
   since its appearance frequency has been increased by the introduction of another commit
   for fixing an unrelated issue when booting a large memory profile TDX VM.
   (https://lore.kernel.org/all/20250310082855.2587122-1-kirill.shutemov@linux.intel.com/#t)

   Per consequence, to have a better chance to reproduce the issue, run a AMD SNP or TDX VM
   with a certain CPU configuration:

   For AMD SNP,  you can follow the instructions in the submission
   https://lore.kernel.org/all/363f8293-23e3-44d3-8005-b31eb5b7f975@amd.com/#t

   For Intel TDX, we can also reproduce this issue with Intel TDX VM with our 6.14 -intel kernel that has
   TDX feature enabled (since TDX feature is only in kernel main-next for now and not yet released).

[ Where problems could occur ]

 * Performance regression in memory allocation and regression at CPU bring up time.

[ Further information ]

 * It is necessary to backport this patch to Plucky and Oracular kernel since
   the commit that exhibits this deadlock is in Plucky 6.14 and being backported
   to Oracular 6.11 kernel, however as the backport is not trivial, this will be
   coming in a subsequent submission.

v1 -> v2:
 Updated problem section.
 Provenance/SOB added to the patch.
 More explication on Oracular inclusion.
 
Kirill A. Shutemov (1):
  mm/page_alloc: fix deadlock on cpu_hotplug_lock in __accept_page()

 include/linux/mmzone.h |  3 +++
 mm/internal.h          |  1 +
 mm/mm_init.c           |  1 +
 mm/page_alloc.c        | 28 ++++++++++++++++++++++++++--
 4 files changed, 31 insertions(+), 2 deletions(-)

-- 
2.48.1