From: Alexander M. Merritt <alexander@edera.dev>
Date: Thu, 3 Apr 2025 23:22:19 +0000 (+0000)
Subject: x86: drop XSAVEOPT and CLWB build flags
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=87541439838b8d3b30ae1183c03533694b8e5670;p=xen.git

x86: drop XSAVEOPT and CLWB build flags

The new toolchain baseline knows both the XSAVEOPT and CLWB instructions.

It knows CLFLUSHOPT too, so fix up those.

No functional change.

Resolves: https://gitlab.com/xen-project/xen/-/work_items/205
Signed-off-by: "Alexander M. Merritt" <alexander@edera.dev>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
---

diff --git a/xen/arch/x86/arch.mk b/xen/arch/x86/arch.mk
index 3bbaee2a44..8615533697 100644
--- a/xen/arch/x86/arch.mk
+++ b/xen/arch/x86/arch.mk
@@ -11,9 +11,7 @@ CFLAGS += -msoft-float
 $(call cc-options-add,CFLAGS,CC,$(EMBEDDED_EXTRA_CFLAGS))
 $(call cc-option-add,CFLAGS,CC,-Wnested-externs)
 $(call as-option-add,CFLAGS,CC,"rdrand %eax",-DHAVE_AS_RDRAND)
-$(call as-option-add,CFLAGS,CC,"xsaveopt (%rax)",-DHAVE_AS_XSAVEOPT)
 $(call as-option-add,CFLAGS,CC,"rdseed %eax",-DHAVE_AS_RDSEED)
-$(call as-option-add,CFLAGS,CC,"clwb (%rax)",-DHAVE_AS_CLWB)
 $(call as-option-add,CFLAGS,CC,".equ \"x\"$(comma)1",-DHAVE_AS_QUOTED_SYM)
 $(call as-option-add,CFLAGS,CC,"movdiri %rax$(comma)(%rax)",-DHAVE_AS_MOVDIR)
 $(call as-option-add,CFLAGS,CC,"enqcmd (%rax)$(comma)%rax",-DHAVE_AS_ENQCMD)
diff --git a/xen/arch/x86/flushtlb.c b/xen/arch/x86/flushtlb.c
index 65be0474a8..1e0011d5b1 100644
--- a/xen/arch/x86/flushtlb.c
+++ b/xen/arch/x86/flushtlb.c
@@ -287,7 +287,7 @@ void cache_flush(const void *addr, unsigned int size)
          * of letting the alternative framework fill the gap by appending nops.
          */
         alternative_input("ds; clflush %[p]",/* Semicolon for Clang-IAS < 12 */
-                          "data16 clflush %[p]", /* clflushopt */
+                          "clflushopt %[p]",
                            X86_FEATURE_CLFLUSHOPT,
                            [p] "m" (*(const char *)(addr)));
     }
@@ -313,33 +313,7 @@ void cache_writeback(const void *addr, unsigned int size)
     clflush_size = current_cpu_data.x86_clflush_size ?: 16;
     addr -= (unsigned long)addr & (clflush_size - 1);
     for ( ; addr < end; addr += clflush_size )
-    {
-/*
- * The arguments to a macro must not include preprocessor directives. Doing so
- * results in undefined behavior, so we have to create some defines here in
- * order to avoid it.
- */
-#if defined(HAVE_AS_CLWB)
-# define CLWB_ENCODING "clwb %[p]"
-#elif defined(HAVE_AS_XSAVEOPT)
-# define CLWB_ENCODING "data16 xsaveopt %[p]" /* clwb */
-#else
-# define CLWB_ENCODING ".byte 0x66, 0x0f, 0xae, 0x30" /* clwb (%%rax) */
-#endif
-
-#define BASE_INPUT(addr) [p] "m" (*(const char *)(addr))
-#if defined(HAVE_AS_CLWB) || defined(HAVE_AS_XSAVEOPT)
-# define INPUT BASE_INPUT
-#else
-# define INPUT(addr) "a" (addr), BASE_INPUT(addr)
-#endif
-
-        asm volatile (CLWB_ENCODING :: INPUT(addr));
-
-#undef INPUT
-#undef BASE_INPUT
-#undef CLWB_ENCODING
-    }
+        clwb(addr);
 
     asm volatile ("sfence" ::: "memory");
 }
diff --git a/xen/arch/x86/include/asm/system.h b/xen/arch/x86/include/asm/system.h
index 8ceaaf45d1..57446c5b46 100644
--- a/xen/arch/x86/include/asm/system.h
+++ b/xen/arch/x86/include/asm/system.h
@@ -23,19 +23,12 @@ static inline void clflush(const void *p)
 
 static inline void clflushopt(const void *p)
 {
-    asm volatile ( "data16 clflush %0" :: "m" (*(const char *)p) );
+    asm volatile ( "clflushopt %0" :: "m" (*(const char *)p) );
 }
 
 static inline void clwb(const void *p)
 {
-#if defined(HAVE_AS_CLWB)
     asm volatile ( "clwb %0" :: "m" (*(const char *)p) );
-#elif defined(HAVE_AS_XSAVEOPT)
-    asm volatile ( "data16 xsaveopt %0" :: "m" (*(const char *)p) );
-#else
-    asm volatile ( ".byte 0x66, 0x0f, 0xae, 0x32"
-                   :: "d" (p), "m" (*(const char *)p) );
-#endif
 }
 
 #define xchg(ptr,v) \