From: Andrew Cooper <andrew.cooper3@citrix.com>
Date: Fri, 22 Mar 2024 12:08:02 +0000 (+0000)
Subject: x86/spec_ctrl: Hold SCF in %ebx across SPEC_CTRL_ENTRY_{PV,INTR}
X-Git-Tag: RELEASE-4.16.6~12
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=6107fa01870e33ab59969f5f21f959352a3670d5;p=xen.git

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>
(cherry picked from commit 9607aeb6602b8ed9962404de3f5f90170ffddb66)
---

diff --git a/xen/arch/x86/x86_64/compat/entry.S b/xen/arch/x86/x86_64/compat/entry.S
index a32b95f7c3..ff462a92e0 100644
--- a/xen/arch/x86/x86_64/compat/entry.S
+++ b/xen/arch/x86/x86_64/compat/entry.S
@@ -20,7 +20,7 @@ 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
diff --git a/xen/arch/x86/x86_64/entry.S b/xen/arch/x86/x86_64/entry.S
index c52229d032..09f143354e 100644
--- a/xen/arch/x86/x86_64/entry.S
+++ b/xen/arch/x86/x86_64/entry.S
@@ -268,7 +268,7 @@ 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
@@ -306,7 +306,7 @@ 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
@@ -348,7 +348,7 @@ 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). */
@@ -403,7 +403,7 @@ 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
@@ -704,7 +704,7 @@ 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
@@ -738,7 +738,7 @@ 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
diff --git a/xen/include/asm-x86/spec_ctrl_asm.h b/xen/include/asm-x86/spec_ctrl_asm.h
index d536a79f28..de6a6e4ff1 100644
--- a/xen/include/asm-x86/spec_ctrl_asm.h
+++ b/xen/include/asm-x86/spec_ctrl_asm.h
@@ -268,9 +268,11 @@
  */
 .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
 
@@ -294,8 +296,10 @@
 .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