File xsa456-0k.patch of Package xen.35285

# Commit 9607aeb6602b8ed9962404de3f5f90170ffddb66
# Date 2024-04-09 16:37:30 +0100
# Author Andrew Cooper <andrew.cooper3@citrix.com>
# Committer Andrew Cooper <andrew.cooper3@citrix.com>
x86/spec_ctrl: Hold SCF in %ebx across SPEC_CTRL_ENTRY_{PV,INTR}

... as we do in the exit paths too.  This will allow simplification to the
sub-blocks.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

--- a/xen/arch/x86/x86_64/compat/entry.S
+++ b/xen/arch/x86/x86_64/compat/entry.S
@@ -19,7 +19,7 @@ ENTRY(entry_int82)
 
         GET_STACK_END(14)
 
-        SPEC_CTRL_ENTRY_FROM_PV /* Req: %rsp=regs/cpuinfo, %rdx=0, Clob: acd */
+        SPEC_CTRL_ENTRY_FROM_PV /* Req: %rsp=regs/cpuinfo, %r14=end, %rdx=0, Clob: abcd */
         /* WARNING! `ret`, `call *`, `jmp *` not safe before this point. */
 
         sti
@@ -219,7 +219,7 @@ ENTRY(cstar_enter)
 
         GET_STACK_END(14)
 
-        SPEC_CTRL_ENTRY_FROM_PV /* Req: %rsp=regs/cpuinfo, %rdx=0, Clob: acd */
+        SPEC_CTRL_ENTRY_FROM_PV /* Req: %rsp=regs/cpuinfo, %r14=end, %rdx=0, Clob: abcd */
         /* WARNING! `ret`, `call *`, `jmp *` not safe before this point. */
 
         mov   STACK_CPUINFO_FIELD(xen_cr3)(%r14), %rcx
--- a/xen/arch/x86/x86_64/entry.S
+++ b/xen/arch/x86/x86_64/entry.S
@@ -242,7 +242,7 @@ ENTRY(lstar_enter)
 
         GET_STACK_END(14)
 
-        SPEC_CTRL_ENTRY_FROM_PV /* Req: %rsp=regs/cpuinfo, %rdx=0, Clob: acd */
+        SPEC_CTRL_ENTRY_FROM_PV /* Req: %rsp=regs/cpuinfo, %r14=end, %rdx=0, Clob: abcd */
         /* WARNING! `ret`, `call *`, `jmp *` not safe before this point. */
 
         mov   STACK_CPUINFO_FIELD(xen_cr3)(%r14), %rcx
@@ -277,7 +277,7 @@ GLOBAL(sysenter_eflags_saved)
 
         GET_STACK_END(14)
 
-        SPEC_CTRL_ENTRY_FROM_PV /* Req: %rsp=regs/cpuinfo, %rdx=0, Clob: acd */
+        SPEC_CTRL_ENTRY_FROM_PV /* Req: %rsp=regs/cpuinfo, %r14=end, %rdx=0, Clob: abcd */
         /* WARNING! `ret`, `call *`, `jmp *` not safe before this point. */
 
         /* PUSHF above has saved EFLAGS.IF clear (the caller had it set). */
@@ -329,7 +329,7 @@ ENTRY(int80_direct_trap)
 
         GET_STACK_END(14)
 
-        SPEC_CTRL_ENTRY_FROM_PV /* Req: %rsp=regs/cpuinfo, %rdx=0, Clob: acd */
+        SPEC_CTRL_ENTRY_FROM_PV /* Req: %rsp=regs/cpuinfo, %r14=end, %rdx=0, Clob: abcd */
         /* WARNING! `ret`, `call *`, `jmp *` not safe before this point. */
 
         mov   STACK_CPUINFO_FIELD(xen_cr3)(%r14), %rcx
@@ -608,7 +608,7 @@ ENTRY(common_interrupt)
 
         GET_STACK_END(14)
 
-        SPEC_CTRL_ENTRY_FROM_INTR /* Req: %rsp=regs, %r14=end, %rdx=0, Clob: acd */
+        SPEC_CTRL_ENTRY_FROM_INTR /* Req: %rsp=regs, %r14=end, %rdx=0, Clob: abcd */
         /* WARNING! `ret`, `call *`, `jmp *` not safe before this point. */
 
         mov   STACK_CPUINFO_FIELD(xen_cr3)(%r14), %rcx
@@ -640,7 +640,7 @@ GLOBAL(handle_exception)
 
         GET_STACK_END(14)
 
-        SPEC_CTRL_ENTRY_FROM_INTR /* Req: %rsp=regs, %r14=end, %rdx=0, Clob: acd */
+        SPEC_CTRL_ENTRY_FROM_INTR /* Req: %rsp=regs, %r14=end, %rdx=0, Clob: abcd */
         /* WARNING! `ret`, `call *`, `jmp *` not safe before this point. */
 
         mov   STACK_CPUINFO_FIELD(xen_cr3)(%r14), %rcx
--- a/xen/include/asm-x86/spec_ctrl_asm.h
+++ b/xen/include/asm-x86/spec_ctrl_asm.h
@@ -270,9 +270,11 @@
  */
 .macro SPEC_CTRL_ENTRY_FROM_PV
 /*
- * Requires %rsp=regs/cpuinfo, %rdx=0
- * Clobbers %rax, %rcx, %rdx
+ * Requires %rsp=regs/cpuinfo, %r14=stack_end, %rdx=0
+ * Clobbers %rax, %rbx, %rcx, %rdx
  */
+    movzbl STACK_CPUINFO_FIELD(scf)(%r14), %ebx
+
     ALTERNATIVE "", __stringify(DO_SPEC_CTRL_COND_IBPB maybexen=0),     \
         X86_FEATURE_IBPB_ENTRY_PV
 
@@ -296,8 +298,10 @@
 .macro SPEC_CTRL_ENTRY_FROM_INTR
 /*
  * Requires %rsp=regs, %r14=stack_end, %rdx=0
- * Clobbers %rax, %rcx, %rdx
+ * Clobbers %rax, %rbx, %rcx, %rdx
  */
+    movzbl STACK_CPUINFO_FIELD(scf)(%r14), %ebx
+
     testb $3, UREGS_cs(%rsp)
     jz .L\@_skip