Re: [PATCH] livepatch: apply_alternatives() is only used for livepatch

[Julien Grall <julien@xxxxxxx>]

Hi Roger,

On 06/06/2023 18:23, Roger Pau Monne wrote:
> Guard it with CONFIG_LIVEPATCH.  Note alternatives are applied at boot
> using _apply_alternatives().
>
> Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>

> ---
>   xen/arch/arm/alternative.c             | 2 ++
>   xen/arch/arm/include/asm/alternative.h | 2 ++
>   xen/arch/x86/alternative.c             | 5 +++--
>   xen/arch/x86/include/asm/alternative.h | 2 ++
>   4 files changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/xen/arch/arm/alternative.c b/xen/arch/arm/alternative.c
> index 7366af4ea646..016e66978b6d 100644
> --- a/xen/arch/arm/alternative.c
> +++ b/xen/arch/arm/alternative.c
> @@ -223,6 +223,7 @@ void __init apply_alternatives_all(void)
>       vunmap(xenmap);
>   }
>   
> +#ifdef CONFIG_LIVEPATCH
>   int apply_alternatives(const struct alt_instr *start, const struct alt_instr 
> *end)
>   {
>       const struct alt_region region = {
> @@ -232,6 +233,7 @@ int apply_alternatives(const struct alt_instr *start, const 
> struct alt_instr *en
>   
>       return __apply_alternatives(&region, 0);
>   }
> +#endif
>   
>   /*
>    * Local variables:
> diff --git a/xen/arch/arm/include/asm/alternative.h 
> b/xen/arch/arm/include/asm/alternative.h
> index d3210e82f9e5..ce82dc1ca0d2 100644
> --- a/xen/arch/arm/include/asm/alternative.h
> +++ b/xen/arch/arm/include/asm/alternative.h
> @@ -29,7 +29,9 @@ typedef void (*alternative_cb_t)(const struct alt_instr *alt,
>                                  int nr_inst);
>   
>   void apply_alternatives_all(void);
> +#ifdef CONFIG_LIVEPATCH
>   int apply_alternatives(const struct alt_instr *start, const struct alt_instr 
> *end);
> +#endif
>   
>   #define ALTINSTR_ENTRY(feature, cb)					      \
>         " .word 661b - .\n"                           /* label           */ \
> diff --git a/xen/arch/x86/alternative.c b/xen/arch/x86/alternative.c
> index 99482766b51f..21af0e825822 100644
> --- a/xen/arch/x86/alternative.c
> +++ b/xen/arch/x86/alternative.c
> @@ -358,11 +358,12 @@ static void init_or_livepatch _apply_alternatives(struct 
> alt_instr *start,
>       }
>   }
>   
> -void init_or_livepatch apply_alternatives(struct alt_instr *start,
> -                                          struct alt_instr *end)
NIT: It sounds like the init_* was a left-over after commit 67d01cdb5518 
("x86: infrastructure to allow converting certain indirect calls to 
direct ones").
Cheers,

--
Julien Grall