Re: [PATCH 1/1] mm: disable CONFIG_PER_VMA_LOCK by default until its fixed

[David Rientjes <rientjes@google.com>]

On Mon, 3 Jul 2023, Suren Baghdasaryan wrote:

> A memory corruption was reported in [1] with bisection pointing to the
> patch [2] enabling per-VMA locks for x86.
> Disable per-VMA locks config to prevent this issue while the problem is
> being investigated. This is expected to be a temporary measure.
> 
> [1] https://bugzilla.kernel.org/show_bug.cgi?id=217624
> [2] https://lore.kernel.org/all/20230227173632.3292573-30-surenb@google.com
> 
> Reported-by: Jiri Slaby <jirislaby@kernel.org>
> Reported-by: Jacob Young <jacobly.alt@gmail.com>
> Fixes: 0bff0aaea03e ("x86/mm: try VMA lock-based page fault handling first")
> Signed-off-by: Suren Baghdasaryan <surenb@google.com>

Acked-by: David Rientjes <rientjes@google.com>

Thanks for the heads up!  The bisect commit [2] is a no-op with 
CONFIG_PER_VMA_LOCK disabled, this looks good.

Nit: in that patch the "done" label could have been a:
"done: __maybe_unused"
to a avoid the #ifdef :P

> ---
>  mm/Kconfig | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/Kconfig b/mm/Kconfig
> index 09130434e30d..de94b2497600 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -1224,7 +1224,7 @@ config ARCH_SUPPORTS_PER_VMA_LOCK
>         def_bool n
>  
>  config PER_VMA_LOCK
> -	def_bool y
> +	bool "Enable per-vma locking during page fault handling."
>  	depends on ARCH_SUPPORTS_PER_VMA_LOCK && MMU && SMP
>  	help
>  	  Allow per-vma locking during page fault handling.
> -- 
> 2.41.0.255.g8b1d071c50-goog
> 
>