[Xen-devel] [PATCH 1/2] x86: add alternavive_io_2/3 to support alternative with 2/3 features.

[Shuai Ruan <shuai.ruan@xxxxxxxxxxxxxxx>]

Most of the code is porting from linux with some changes.
alternative_io_2 replaces old instruction with new instructions
based on two features.
alternative_io_3 replaces old instruction with new instructions
based on three features.

Signed-off-by: Shuai Ruan <shuai.ruan@xxxxxxxxxxxxxxx>
---
 xen/include/asm-x86/alternative.h | 65 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 65 insertions(+)

diff --git a/xen/include/asm-x86/alternative.h 
b/xen/include/asm-x86/alternative.h
index 7d11354..b018613 100644
--- a/xen/include/asm-x86/alternative.h
+++ b/xen/include/asm-x86/alternative.h
@@ -59,6 +59,39 @@ extern void alternative_instructions(void);
         ALTINSTR_REPLACEMENT(newinstr, feature, 1)                      \
         ".popsection"
 
+#define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \
+        OLDINSTR(oldinstr)                                                \
+        ".pushsection .altinstructions,\"a\"\n"                           \
+        ALTINSTR_ENTRY(feature1, 1)                                       \
+        ALTINSTR_ENTRY(feature2, 2)                                       \
+        ".popsection\n"                                                   \
+        ".pushsection .discard,\"aw\",@progbits\n"                        \
+        DISCARD_ENTRY(1)                                                  \
+        DISCARD_ENTRY(2)                                                  \
+        ".popsection\n"                                                   \
+        ".pushsection .altinstr_replacement, \"ax\"\n"                    \
+        ALTINSTR_REPLACEMENT(newinstr1, feature1, 1)                      \
+        ALTINSTR_REPLACEMENT(newinstr2, feature2, 2)                      \
+        ".popsection"
+
+#define ALTERNATIVE_3(oldinstr, newinstr1, feature1, newinstr2, feature2, \
+                      newinstr3, feature3)                                \
+        OLDINSTR(oldinstr)                                                \
+        ".pushsection .altinstructions,\"a\"\n"                           \
+        ALTINSTR_ENTRY(feature1, 1)                                       \
+        ALTINSTR_ENTRY(feature2, 2)                                       \
+        ALTINSTR_ENTRY(feature3, 3)                                       \
+        ".popsection\n"                                                   \
+        ".pushsection .discard,\"aw\",@progbits\n"                        \
+        DISCARD_ENTRY(1)                                                  \
+        DISCARD_ENTRY(2)                                                  \
+        DISCARD_ENTRY(3)                                                  \
+        ".popsection\n"                                                   \
+        ".pushsection .altinstr_replacement, \"ax\"\n"                    \
+        ALTINSTR_REPLACEMENT(newinstr1, feature1, 1)                      \
+        ALTINSTR_REPLACEMENT(newinstr2, feature2, 2)                      \
+        ALTINSTR_REPLACEMENT(newinstr3, feature3, 3)                      \
+        ".popsection"
 /*
  * Alternative instructions for different CPU types or capabilities.
  *
@@ -93,6 +126,38 @@ extern void alternative_instructions(void);
        asm volatile (ALTERNATIVE(oldinstr, newinstr, feature)          \
                      : output : input)
 
+/*
+ *  This is similar to alternative_io. But it has two features and
+ *  respective instructions.
+ *
+ *  If CPU has feature2, newinstr2 is used.
+ *  if CPU has feature1, newinstr1 is used.
+ *  Otherwise, oldinstr is used.
+ */
+
+#define alternative_io_2(oldinstr, newinstr1, feature1, newinstr2,       \
+                         feature2, out_put, input...)                    \
+        asm volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1,        \
+                     newinstr2, feature2)                                \
+                     : output : input)
+
+/*
+ *  This is similar to alternative_io. But it has three features and
+ *  respective instructions.
+ *
+ *  If CPU has feature3, newinstr3 is used.
+ *  If CPU has feature2, newinstr2 is used.
+ *  if CPU has feature1, newinstr1 is used.
+ *  Otherwise, oldinstr is used.
+ */
+
+#define alternative_io_3(oldinstr, newinstr1, feature1, newinstr2,       \
+                         feature2, newinstr3, feature3, output,          \
+                         input...)                                       \
+        asm volatile(ALTERNATIVE_3(oldinstr, newinstr1, feature1,        \
+                     newinstr2, feature2, newinstr3, feature3)           \
+                     : output : input)
+
 /* Use this macro(s) if you need more than one output parameter. */
 #define ASM_OUTPUT2(a...) a
 
-- 
1.9.1


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