[PATCH v6 05/12] x86/alternative: support ALTERNATIVE_TERNARY

[Juergen Gross <jgross@xxxxxxxx>]

Add ALTERNATIVE_TERNARY support for replacing an initial instruction
with either of two instructions depending on a feature:

  ALTERNATIVE_TERNARY "default_instr", FEATURE_NR,
                      "feature_on_instr", "feature_off_instr"

which will start with "default_instr" and at patch time will, depending
on FEATURE_NR being set or not, patch that with either
"feature_on_instr" or "feature_off_instr".

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
V3:
- new patch
V4:
- use X86_FEATURE_ALWAYS instead of negated feature (Boris Petkov)
- unfortunately this isn't enough to get rid of the "not feature"
  support, as this is needed in the patch "x86/paravirt: switch
  functions with custom code to ALTERNATIVE", too
V5:
- carve out the "not feature" part
---
 arch/x86/include/asm/alternative-asm.h | 4 ++++
 arch/x86/include/asm/alternative.h     | 6 ++++++
 2 files changed, 10 insertions(+)

diff --git a/arch/x86/include/asm/alternative-asm.h 
b/arch/x86/include/asm/alternative-asm.h
index 3965daf0460e..80bc6b533358 100644
--- a/arch/x86/include/asm/alternative-asm.h
+++ b/arch/x86/include/asm/alternative-asm.h
@@ -112,6 +112,10 @@
        .popsection
 .endm
 
+#define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr1, newinstr2)   \
+       ALTERNATIVE_2 oldinstr, newinstr2, X86_FEATURE_ALWAYS,          \
+       newinstr1, feature
+
 #endif  /*  __ASSEMBLY__  */
 
 #endif /* _ASM_X86_ALTERNATIVE_ASM_H */
diff --git a/arch/x86/include/asm/alternative.h 
b/arch/x86/include/asm/alternative.h
index 89889618ae01..4fb844e29d26 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -178,6 +178,9 @@ static inline int alternatives_text_reserved(void *start, 
void *end)
        ALTINSTR_REPLACEMENT(newinstr2, 2)                              \
        ".popsection\n"
 
+#define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr1, newinstr2)   \
+       ALTERNATIVE_2(oldinstr, newinstr2, X86_FEATURE_ALWAYS, newinstr1, 
feature)
+
 #define ALTERNATIVE_3(oldinsn, newinsn1, feat1, newinsn2, feat2, newinsn3, 
feat3) \
        OLDINSTR_3(oldinsn, 1, 2, 3)                                            
\
        ".pushsection .altinstructions,\"a\"\n"                                 
\
@@ -209,6 +212,9 @@ static inline int alternatives_text_reserved(void *start, 
void *end)
 #define alternative_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \
        asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, 
newinstr2, feature2) ::: "memory")
 
+#define alternative_ternary(oldinstr, feature, newinstr1, newinstr2)   \
+       asm_inline volatile(ALTERNATIVE_TERNARY(oldinstr, feature, newinstr1, 
newinstr2) ::: "memory")
+
 /*
  * Alternative inline assembly with input.
  *
-- 
2.26.2