Re: [PATCH v3 3/6] crash hp: definitions and prototype changes

[Eric DeVolder]

Baoquan,
Thanks for looking at this. Inline responses below.
eric

On 1/19/22 02:26, Baoquan He wrote:
> On 01/10/22 at 02:57pm, Eric DeVolder wrote:
> > This change adds members to struct kimage to facilitate crash
> > hotplug support.
> >
> > This change also defines crash hotplug events and associated
> > prototypes.
> >
> > Signed-off-by: Eric DeVolder <eric.devolder@xxxxxxxxxx>
> > ---
> >   include/linux/kexec.h | 21 +++++++++++++++++++--
> >   1 file changed, 19 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/linux/kexec.h b/include/linux/kexec.h
> > index 0c994ae37729..068f853f1c65 100644
> > --- a/include/linux/kexec.h
> > +++ b/include/linux/kexec.h
> > @@ -221,8 +221,9 @@ struct crash_mem {
> >   extern int crash_exclude_mem_range(struct crash_mem *mem,
> >   				   unsigned long long mstart,
> >   				   unsigned long long mend);
> > -extern int crash_prepare_elf64_headers(struct crash_mem *mem, int kernel_map,
> > -				       void **addr, unsigned long *sz);
> > +extern int crash_prepare_elf64_headers(struct kimage *image,
> > +					struct crash_mem *mem, int kernel_map,
> > +					void **addr, unsigned long *sz);
> >   #endif /* CONFIG_KEXEC_FILE */
> >   
> >   #ifdef CONFIG_KEXEC_ELF
> > @@ -299,6 +300,13 @@ struct kimage {
> >   
> >   	/* Information for loading purgatory */
> >   	struct purgatory_info purgatory_info;
> > +
> > +#ifdef CONFIG_CRASH_HOTPLUG
> > +	bool hotplug_event;
> > +	int offlinecpu;
> > +	bool elf_index_valid;
> > +	int elf_index;
>
> Do we really need elf_index_valid? Can we initialize elf_index to , e.g '-1',
> then check if the value is valid?

These members become part of struct kimage, and when the kimage is allocated, it is automatically 
zero'd. Wrt/ elf_index, 0 is a valid index, and so it needs to be qualified. I initially had used 
-1, but that required code and was fragile as I had to find the right place to do that. Using the 
boolean elf_index_valid, the problems with -1 vanish, and for free! I also found when examining the 
code that reading 'elf_index_valid' was better than 'elf_index != -1', more clear.

Let me know what you think.
eric

> > +#endif
> >   #endif
> >   
> >   #ifdef CONFIG_IMA_KEXEC
> > @@ -315,6 +323,15 @@ struct kimage {
> >   	unsigned long elf_load_addr;
> >   };
> >   
> > +#ifdef CONFIG_CRASH_HOTPLUG
> > +void arch_crash_hotplug_handler(struct kimage *image,
> > +	unsigned int hp_action, unsigned long a, unsigned long b);
> > +#define KEXEC_CRASH_HP_REMOVE_CPU   0
> > +#define KEXEC_CRASH_HP_ADD_CPU      1
> > +#define KEXEC_CRASH_HP_REMOVE_MEMORY 2
> > +#define KEXEC_CRASH_HP_ADD_MEMORY   3
> > +#endif /* CONFIG_CRASH_HOTPLUG */
> > +
> >   /* kexec interface functions */
> >   extern void machine_kexec(struct kimage *image);
> >   extern int machine_kexec_prepare(struct kimage *image);
> > --
> > 2.27.0