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

[Jacob Martin]

On 5/15/25 11:49 AM, Thibault Ferrante wrote:
> 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(-)
> 

Acked-by: Jacob Martin <jacob.martin at canonical.com>