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

[Julien Grall]

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....@citrix.com>

Reviewed-by: Julien Grall <jgr...@amazon.com>

---
  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