[PATCH 1/9] x86/spec-ctrl: Fix confusion between SPEC_CTRL_EXIT_TO_XEN{,_IST}

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

c/s 3fffaf9c13e9 ("x86/entry: Avoid using alternatives in NMI/#MC paths")
dropped the only user, leaving behind the (incorrect) implication that Xen had
split exit paths.

Delete the unused SPEC_CTRL_EXIT_TO_XEN and rename SPEC_CTRL_EXIT_TO_XEN_IST
to SPEC_CTRL_EXIT_TO_XEN for consistency.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>

v2:
 * Tweak comment.
---
 xen/arch/x86/include/asm/spec_ctrl_asm.h | 10 ++--------
 xen/arch/x86/x86_64/entry.S              |  2 +-
 2 files changed, 3 insertions(+), 9 deletions(-)

diff --git a/xen/arch/x86/include/asm/spec_ctrl_asm.h 
b/xen/arch/x86/include/asm/spec_ctrl_asm.h
index f48f9e75e8dc..cfba35560333 100644
--- a/xen/arch/x86/include/asm/spec_ctrl_asm.h
+++ b/xen/arch/x86/include/asm/spec_ctrl_asm.h
@@ -67,7 +67,6 @@
  *  - SPEC_CTRL_ENTRY_FROM_PV
  *  - SPEC_CTRL_ENTRY_FROM_INTR
  *  - SPEC_CTRL_ENTRY_FROM_INTR_IST
- *  - SPEC_CTRL_EXIT_TO_XEN_IST
  *  - SPEC_CTRL_EXIT_TO_XEN
  *  - SPEC_CTRL_EXIT_TO_PV
  *
@@ -256,11 +255,6 @@
     ALTERNATIVE "", __stringify(DO_SPEC_CTRL_ENTRY maybexen=1),         \
         X86_FEATURE_SC_MSR_PV
 
-/* Use when exiting to Xen context. */
-#define SPEC_CTRL_EXIT_TO_XEN                                           \
-    ALTERNATIVE "",                                                     \
-        DO_SPEC_CTRL_EXIT_TO_XEN, X86_FEATURE_SC_MSR_PV
-
 /* Use when exiting to PV guest context. */
 #define SPEC_CTRL_EXIT_TO_PV                                            \
     ALTERNATIVE "",                                                     \
@@ -327,8 +321,8 @@ UNLIKELY_DISPATCH_LABEL(\@_serialise):
     UNLIKELY_END(\@_serialise)
 .endm
 
-/* Use when exiting to Xen in IST context. */
-.macro SPEC_CTRL_EXIT_TO_XEN_IST
+/* Use when exiting to Xen context. */
+.macro SPEC_CTRL_EXIT_TO_XEN
 /*
  * Requires %rbx=stack_end
  * Clobbers %rax, %rcx, %rdx
diff --git a/xen/arch/x86/x86_64/entry.S b/xen/arch/x86/x86_64/entry.S
index 81dd2c74b876..a1c860f56949 100644
--- a/xen/arch/x86/x86_64/entry.S
+++ b/xen/arch/x86/x86_64/entry.S
@@ -673,7 +673,7 @@ UNLIKELY_START(ne, exit_cr3)
 UNLIKELY_END(exit_cr3)
 
         /* WARNING! `ret`, `call *`, `jmp *` not safe beyond this point. */
-        SPEC_CTRL_EXIT_TO_XEN_IST /* Req: %rbx=end, Clob: acd */
+        SPEC_CTRL_EXIT_TO_XEN     /* Req: %rbx=end, Clob: acd */
 
         RESTORE_ALL adj=8
         iretq
-- 
2.30.2