[Xen-devel] [PATCH 1/5] arm/alternatives: Fix apply_alternatives() API

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

The !HAS_ALTERNATIVE case has bit-rotten and won't even compile.

The x86 side of apply_alternatives() is void, while the ARM side returns int.
However, the functions can't fail and no return values are checked.  Switch
the ARM side to be void as well.

One observation is that __apply_alternatives_multi_stop() is only used at boot
time, so can become __init and its static data can become __initdata

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
CC: Julien Grall <julien.grall@xxxxxxx>
CC: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
CC: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>

TODO: Drop the !HAS_ALTERNATIVE case on ARM?
---
 xen/arch/arm/alternative.c        | 18 +++++++-----------
 xen/include/asm-arm/alternative.h |  7 ++++---
 2 files changed, 11 insertions(+), 14 deletions(-)

diff --git a/xen/arch/arm/alternative.c b/xen/arch/arm/alternative.c
index 9ffdc47..99112e1 100644
--- a/xen/arch/arm/alternative.c
+++ b/xen/arch/arm/alternative.c
@@ -98,7 +98,7 @@ static u32 get_alt_insn(const struct alt_instr *alt,
  * The region patched should be read-write to allow __apply_alternatives
  * to replacing the instructions when necessary.
  */
-static int __apply_alternatives(const struct alt_region *region)
+static void __apply_alternatives(const struct alt_region *region)
 {
     const struct alt_instr *alt;
     const u32 *replptr;
@@ -135,17 +135,15 @@ static int __apply_alternatives(const struct alt_region 
*region)
 
     /* Nuke the instruction cache */
     invalidate_icache();
-
-    return 0;
 }
 
 /*
  * We might be patching the stop_machine state machine, so implement a
  * really simple polling protocol here.
  */
-static int __apply_alternatives_multi_stop(void *unused)
+static int __init __apply_alternatives_multi_stop(void *unused)
 {
-    static int patched = 0;
+    static int __initdata patched = 0;
 
     /* We always have a CPU 0 at this point (__init) */
     if ( smp_processor_id() )
@@ -156,7 +154,6 @@ static int __apply_alternatives_multi_stop(void *unused)
     }
     else
     {
-        int ret;
         struct alt_region region;
         mfn_t xen_mfn = virt_to_mfn(_start);
         paddr_t xen_size = _end - _start;
@@ -196,9 +193,7 @@ static int __apply_alternatives_multi_stop(void *unused)
         region.begin = (void *)__alt_instructions - (void *)_start + xenmap;
         region.end = (void *)__alt_instructions_end - (void *)_start + xenmap;
 
-        ret = __apply_alternatives(&region);
-        /* The patching is not expected to fail during boot. */
-        BUG_ON(ret != 0);
+        __apply_alternatives(&region);
 
         unregister_virtual_region(&patch_region);
 
@@ -228,14 +223,15 @@ void __init apply_alternatives_all(void)
     BUG_ON(ret);
 }
 
-int apply_alternatives(const struct alt_instr *start, const struct alt_instr 
*end)
+void apply_alternatives(const struct alt_instr *start,
+                        const struct alt_instr *end)
 {
     const struct alt_region region = {
         .begin = start,
         .end = end,
     };
 
-    return __apply_alternatives(&region);
+    __apply_alternatives(&region);
 }
 
 /*
diff --git a/xen/include/asm-arm/alternative.h 
b/xen/include/asm-arm/alternative.h
index 6cc9d0d..49a055e 100644
--- a/xen/include/asm-arm/alternative.h
+++ b/xen/include/asm-arm/alternative.h
@@ -25,7 +25,8 @@ struct alt_instr {
 #define ALT_REPL_PTR(a)                __ALT_PTR(a, alt_offset)
 
 void __init apply_alternatives_all(void);
-int apply_alternatives(const struct alt_instr *start, const struct alt_instr 
*end);
+void apply_alternatives(const struct alt_instr *start,
+                        const struct alt_instr *end);
 
 #define ALTINSTR_ENTRY(feature)                                                
      \
        " .word 661b - .\n"                             /* label           */ \
@@ -158,9 +159,9 @@ static inline void apply_alternatives_all(void)
 {
 }
 
-static inline int apply_alternatives(void *start, size_t length)
+static inline void apply_alternatives(const struct alt_instr *start,
+                                      const struct alt_instr *end)
 {
-    return 0;
 }
 
 #endif
-- 
2.1.4


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