[PATCH v2 2/6] x86/msr: remove HAVE_AS_FSGSBASE

[dmkhn@xxxxxxxxx]

From: Denis Mukhin <dmukhin@xxxxxxxx>

The new toolchain baseline knows the {rd,wr}{f,g}sbase instructions,
no need to carry the workaround in the code.

Resolves: https://gitlab.com/xen-project/xen/-/work_items/207
Signed-off-by: Denis Mukhin <dmukhin@xxxxxxxx>
---
 xen/arch/x86/arch.mk           |  1 -
 xen/arch/x86/include/asm/msr.h | 22 ----------------------
 2 files changed, 23 deletions(-)

diff --git a/xen/arch/x86/arch.mk b/xen/arch/x86/arch.mk
index e9fa1c92d7..6d2876b1a8 100644
--- a/xen/arch/x86/arch.mk
+++ b/xen/arch/x86/arch.mk
@@ -12,7 +12,6 @@ $(call cc-options-add,CFLAGS,CC,$(EMBEDDED_EXTRA_CFLAGS))
 $(call cc-option-add,CFLAGS,CC,-Wnested-externs)
 $(call as-option-add,CFLAGS,CC,"crc32 %eax$(comma)%eax",-DHAVE_AS_SSE4_2)
 $(call as-option-add,CFLAGS,CC,"rdrand %eax",-DHAVE_AS_RDRAND)
-$(call as-option-add,CFLAGS,CC,"rdfsbase %rax",-DHAVE_AS_FSGSBASE)
 $(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)
diff --git a/xen/arch/x86/include/asm/msr.h b/xen/arch/x86/include/asm/msr.h
index 549d40b404..0d3b1d6374 100644
--- a/xen/arch/x86/include/asm/msr.h
+++ b/xen/arch/x86/include/asm/msr.h
@@ -152,11 +152,7 @@ static inline unsigned long __rdfsbase(void)
 {
     unsigned long base;
 
-#ifdef HAVE_AS_FSGSBASE
     asm volatile ( "rdfsbase %0" : "=r" (base) );
-#else
-    asm volatile ( ".byte 0xf3, 0x48, 0x0f, 0xae, 0xc0" : "=a" (base) );
-#endif
 
     return base;
 }
@@ -165,31 +161,19 @@ static inline unsigned long __rdgsbase(void)
 {
     unsigned long base;
 
-#ifdef HAVE_AS_FSGSBASE
     asm volatile ( "rdgsbase %0" : "=r" (base) );
-#else
-    asm volatile ( ".byte 0xf3, 0x48, 0x0f, 0xae, 0xc8" : "=a" (base) );
-#endif
 
     return base;
 }
 
 static inline void __wrfsbase(unsigned long base)
 {
-#ifdef HAVE_AS_FSGSBASE
     asm volatile ( "wrfsbase %0" :: "r" (base) );
-#else
-    asm volatile ( ".byte 0xf3, 0x48, 0x0f, 0xae, 0xd0" :: "a" (base) );
-#endif
 }
 
 static inline void __wrgsbase(unsigned long base)
 {
-#ifdef HAVE_AS_FSGSBASE
     asm volatile ( "wrgsbase %0" :: "r" (base) );
-#else
-    asm volatile ( ".byte 0xf3, 0x48, 0x0f, 0xae, 0xd8" :: "a" (base) );
-#endif
 }
 
 static inline unsigned long read_fs_base(void)
@@ -253,15 +237,9 @@ static inline void write_gs_shadow(unsigned long base)
     if ( read_cr4() & X86_CR4_FSGSBASE )
     {
         asm volatile ( "swapgs\n\t"
-#ifdef HAVE_AS_FSGSBASE
                        "wrgsbase %0\n\t"
                        "swapgs"
                        :: "r" (base) );
-#else
-                       ".byte 0xf3, 0x48, 0x0f, 0xae, 0xd8\n\t"
-                       "swapgs"
-                       :: "a" (base) );
-#endif
     }
     else
         wrmsrl(MSR_SHADOW_GS_BASE, base);
-- 
2.34.1