Re: [PATCH v2 1/2] kexec: Add KEXEC_FILE_NO_CMA as a legal flag

[Andrew Morton <akpm@linux-foundation.org>]

On Tue, 5 Aug 2025 14:15:26 -0700 Brian Mak <makb@juniper.net> wrote:

> Commit 07d24902977e ("kexec: enable CMA based contiguous allocation")
> introduces logic to use CMA-based allocation in kexec by default. As
> part of the changes, it introduces a kexec_file_load flag to disable the
> use of CMA allocations from userspace. However, this flag is broken
> since it is missing from the list of legal flags for kexec_file_load.
> kexec_file_load returns EINVAL when attempting to use the flag.
> 
> Fix this by adding the KEXEC_FILE_NO_CMA flag to the list of legal flags
> for kexec_file_load.
> 
> Fixes: 07d24902977e ("kexec: enable CMA based contiguous allocation")

A description of the userspace-visible runtime effects of this bug
would be very helpful, please.  A lot more than "is broken"!

Also, could we please have some reviewer input on this change?

Thanks.

> --- a/include/linux/kexec.h
> +++ b/include/linux/kexec.h
> @@ -460,7 +460,8 @@ bool kexec_load_permitted(int kexec_image_type);
>  
>  /* List of defined/legal kexec file flags */
>  #define KEXEC_FILE_FLAGS	(KEXEC_FILE_UNLOAD | KEXEC_FILE_ON_CRASH | \
> -				 KEXEC_FILE_NO_INITRAMFS | KEXEC_FILE_DEBUG)
> +				 KEXEC_FILE_NO_INITRAMFS | KEXEC_FILE_DEBUG | \
> +				 KEXEC_FILE_NO_CMA)
>  
>  /* flag to track if kexec reboot is in progress */
>  extern bool kexec_in_progress;
> -- 
> 2.25.1
>