Re: [PATCH v12 7/7] x86/crash: Add x86 crash hotplug support

[Eric DeVolder]

On 10/28/22 15:30, Borislav Petkov wrote:
> On Fri, Oct 28, 2022 at 02:26:58PM -0500, Eric DeVolder wrote:
> > config CRASH_MAX_MEMORY_RANGES
> >      depends on CRASH_DUMP && KEXEC_FILE && MEMORY_HOTPLUG
> >      int
> >      default 8192
> >      help
> >        For the kexec_file_load path, specify the maximum number of
> >        memory regions, eg. as represented by the 'System RAM' entries
> >        in /proc/iomem, that the elfcorehdr buffer/segment can accommodate.
> >        This value is combined with NR_CPUS and multiplied by Elf64_Phdr
> >        size to determine the final buffer size.
>
> No, do this:
>
> config CRASH_MEMORY_HOTPLUG_SUPPORT
>      depends on CRASH_DUMP && KEXEC_FILE && MEMORY_HOTPLUG
>      help
>        Help text explaining what this feature is
>
> this thing will simply get enabled when the user enables MEMORY_HOTPLUG
> and CRASH_DUMP.
>
> and then you do in the code:
>
> /*
>   * A comment explaining how the 8192 value has been selected.
>   */
> #define CRASH_MAX_MEMORY_RANGES	8192
>
> Thx.

How is this comment?

/*
 * For the kexec_file_load() syscall path, specify the maximum number of
 * memory regions that the elfcorehdr buffer/segment can accommodate.
 * These regions are obtained via walk_system_ram_res(); eg. the
 * 'System RAM' entries in /proc/iomem.
 * This value is combined with NR_CPUS and multiplied by sizeof(Elf64_Phdr)
 * to determine the final elfcorehdr memory buffer/segment size.
 * The value 8192, for example, covers a (sparsely populated) 1TiB system
 * consisting of 128MiB memblock size, while resulting in an elfcorehdr
 * memory buffer/segment size under 1MiB.
 */
#define CRASH_MAX_MEMORY_RANGES 8192