# Commit d9822b8a38114e96e4516dc998f4055249364d5d
# Date 2018-05-16 12:19:10 +0100
# Author Andrew Cooper <andrew.cooper3@citrix.com>
# Committer Andrew Cooper <andrew.cooper3@citrix.com>
x86/spec_ctrl: Rename bits of infrastructure to avoid NATIVE and VMEXIT

In hindsight, using NATIVE and VMEXIT as naming terminology was not clever.
A future change wants to split SPEC_CTRL_EXIT_TO_GUEST into PV and HVM
specific implementations, and using VMEXIT as a term is completely wrong.

Take the opportunity to fix some stale documentation in spec_ctrl_asm.h.  The
IST helpers were missing from the large comment block, and since
SPEC_CTRL_ENTRY_FROM_INTR_IST was introduced, we've gained a new piece of
functionality which currently depends on the fine grain control, which exists
in lieu of livepatching.  Note this in the comment.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

--- a/xen/arch/x86/hvm/svm/entry.S
+++ b/xen/arch/x86/hvm/svm/entry.S
@@ -80,7 +80,7 @@ UNLIKELY_END(svm_trace)
         mov VCPU_arch_spec_ctrl(%rbx), %eax
 
         /* WARNING! `ret`, `call *`, `jmp *` not safe beyond this point. */
-        SPEC_CTRL_EXIT_TO_GUEST /* Req: a=spec_ctrl %rsp=regs/cpuinfo, Clob: cd */
+        SPEC_CTRL_EXIT_TO_HVM   /* Req: a=spec_ctrl %rsp=regs/cpuinfo, Clob: cd */
 
         pop  %r15
         pop  %r14
@@ -105,7 +105,7 @@ UNLIKELY_END(svm_trace)
 
         GET_CURRENT(bx)
 
-        SPEC_CTRL_ENTRY_FROM_VMEXIT /* Req: b=curr %rsp=regs/cpuinfo, Clob: acd */
+        SPEC_CTRL_ENTRY_FROM_HVM    /* Req: b=curr %rsp=regs/cpuinfo, Clob: acd */
         /* WARNING! `ret`, `call *`, `jmp *` not safe before this point. */
 
         mov  VCPU_svm_vmcb(%rbx),%rcx
--- a/xen/arch/x86/hvm/vmx/entry.S
+++ b/xen/arch/x86/hvm/vmx/entry.S
@@ -36,7 +36,7 @@ ENTRY(vmx_asm_vmexit_handler)
         movb $1,VCPU_vmx_launched(%rbx)
         mov  %rax,VCPU_hvm_guest_cr2(%rbx)
 
-        SPEC_CTRL_ENTRY_FROM_VMEXIT /* Req: b=curr %rsp=regs/cpuinfo, Clob: acd */
+        SPEC_CTRL_ENTRY_FROM_HVM    /* Req: b=curr %rsp=regs/cpuinfo, Clob: acd */
         /* WARNING! `ret`, `call *`, `jmp *` not safe before this point. */
 
         mov  %rsp,%rdi
@@ -71,7 +71,7 @@ UNLIKELY_END(realmode)
         mov VCPU_arch_spec_ctrl(%rbx), %eax
 
         /* WARNING! `ret`, `call *`, `jmp *` not safe beyond this point. */
-        SPEC_CTRL_EXIT_TO_GUEST /* Req: a=spec_ctrl %rsp=regs/cpuinfo, Clob: cd */
+        SPEC_CTRL_EXIT_TO_HVM   /* Req: a=spec_ctrl %rsp=regs/cpuinfo, Clob: cd */
 
         mov  VCPU_hvm_guest_cr2(%rbx),%rax
 
--- a/xen/arch/x86/spec_ctrl.c
+++ b/xen/arch/x86/spec_ctrl.c
@@ -35,8 +35,8 @@ static enum ind_thunk {
     THUNK_JMP,
 } opt_thunk __initdata = THUNK_DEFAULT;
 static int8_t __initdata opt_ibrs = -1;
-static bool __initdata opt_rsb_native = true;
-static bool __initdata opt_rsb_vmexit = true;
+static bool __initdata opt_rsb_pv = true;
+static bool __initdata opt_rsb_hvm = true;
 bool __read_mostly opt_ibpb = true;
 uint8_t __read_mostly default_xen_spec_ctrl;
 uint8_t __read_mostly default_spec_ctrl_flags;
@@ -69,9 +69,9 @@ static int __init parse_bti(const char *
         else if ( (val = parse_boolean("ibpb", s, ss)) >= 0 )
             opt_ibpb = val;
         else if ( (val = parse_boolean("rsb_native", s, ss)) >= 0 )
-            opt_rsb_native = val;
+            opt_rsb_pv = val;
         else if ( (val = parse_boolean("rsb_vmexit", s, ss)) >= 0 )
-            opt_rsb_vmexit = val;
+            opt_rsb_hvm = val;
         else
             rc = -EINVAL;
 
@@ -116,8 +116,8 @@ static void __init print_details(enum in
            default_xen_spec_ctrl & SPEC_CTRL_IBRS    ? " IBRS+" :
                                                        " IBRS-"      : "",
            opt_ibpb                                  ? " IBPB"       : "",
-           boot_cpu_has(X86_FEATURE_RSB_NATIVE)      ? " RSB_NATIVE" : "",
-           boot_cpu_has(X86_FEATURE_RSB_VMEXIT)      ? " RSB_VMEXIT" : "");
+           boot_cpu_has(X86_FEATURE_SC_RSB_PV)       ? " RSB_NATIVE" : "",
+           boot_cpu_has(X86_FEATURE_SC_RSB_HVM)      ? " RSB_VMEXIT" : "");
 
     printk("XPTI: %s\n",
            boot_cpu_has(X86_FEATURE_NO_XPTI) ? "disabled" : "enabled");
@@ -307,9 +307,9 @@ void __init init_speculation_mitigations
      * If a processors speculates to 32bit PV guest kernel mappings, it is
      * speculating in 64bit supervisor mode, and can leak data.
      */
-    if ( opt_rsb_native )
+    if ( opt_rsb_pv )
     {
-        setup_force_cpu_cap(X86_FEATURE_RSB_NATIVE);
+        setup_force_cpu_cap(X86_FEATURE_SC_RSB_PV);
         default_spec_ctrl_flags |= SCF_ist_rsb;
     }
 
@@ -317,8 +317,8 @@ void __init init_speculation_mitigations
      * HVM guests can always poison the RSB to point at Xen supervisor
      * mappings.
      */
-    if ( opt_rsb_vmexit )
-        setup_force_cpu_cap(X86_FEATURE_RSB_VMEXIT);
+    if ( opt_rsb_hvm )
+        setup_force_cpu_cap(X86_FEATURE_SC_RSB_HVM);
 
     /* Check we have hardware IBPB support before using it... */
     if ( !boot_cpu_has(X86_FEATURE_IBRSB) && !boot_cpu_has(X86_FEATURE_IBPB) )
--- a/xen/arch/x86/x86_64/compat/entry.S
+++ b/xen/arch/x86/x86_64/compat/entry.S
@@ -163,7 +163,7 @@ ENTRY(compat_restore_all_guest)
         mov VCPU_arch_spec_ctrl(%rbx), %eax
 
         /* WARNING! `ret`, `call *`, `jmp *` not safe beyond this point. */
-        SPEC_CTRL_EXIT_TO_GUEST /* Req: a=spec_ctrl %rsp=regs/cpuinfo, Clob: cd */
+        SPEC_CTRL_EXIT_TO_PV    /* Req: a=spec_ctrl %rsp=regs/cpuinfo, Clob: cd */
 
         RESTORE_ALL adj=8 compat=1
 .Lft0:  iretq
--- a/xen/arch/x86/x86_64/entry.S
+++ b/xen/arch/x86/x86_64/entry.S
@@ -193,7 +193,7 @@ restore_all_guest:
         mov   %r15d, %eax
 
         /* WARNING! `ret`, `call *`, `jmp *` not safe beyond this point. */
-        SPEC_CTRL_EXIT_TO_GUEST /* Req: a=spec_ctrl %rsp=regs/cpuinfo, Clob: cd */
+        SPEC_CTRL_EXIT_TO_PV    /* Req: a=spec_ctrl %rsp=regs/cpuinfo, Clob: cd */
 
         RESTORE_ALL
         testw $TRAP_syscall,4(%rsp)
--- a/xen/include/asm-x86/cpufeatures.h
+++ b/xen/include/asm-x86/cpufeatures.h
@@ -29,6 +29,6 @@ XEN_CPUFEATURE(IND_THUNK_LFENCE,(FSCAPIN
 XEN_CPUFEATURE(IND_THUNK_JMP,   (FSCAPINTS+0)*32+16) /* Use IND_THUNK_JMP */
 XEN_CPUFEATURE(XEN_IBPB,        (FSCAPINTS+0)*32+17) /* IBRSB || IBPB */
 XEN_CPUFEATURE(SC_MSR,          (FSCAPINTS+0)*32+18) /* MSR_SPEC_CTRL used by Xen */
-XEN_CPUFEATURE(RSB_NATIVE,      (FSCAPINTS+0)*32+20) /* RSB overwrite needed for native */
-XEN_CPUFEATURE(RSB_VMEXIT,      (FSCAPINTS+0)*32+21) /* RSB overwrite needed for vmexit */
+XEN_CPUFEATURE(SC_RSB_PV,       (FSCAPINTS+0)*32+20) /* RSB overwrite needed for PV */
+XEN_CPUFEATURE(SC_RSB_HVM,      (FSCAPINTS+0)*32+21) /* RSB overwrite needed for HVM */
 XEN_CPUFEATURE(NO_XPTI,         (FSCAPINTS+0)*32+22) /* XPTI mitigation not in use */
--- a/xen/include/asm-x86/spec_ctrl_asm.h
+++ b/xen/include/asm-x86/spec_ctrl_asm.h
@@ -72,11 +72,14 @@
  *
  * The following ASM fragments implement this algorithm.  See their local
  * comments for further details.
- *  - SPEC_CTRL_ENTRY_FROM_VMEXIT
+ *  - SPEC_CTRL_ENTRY_FROM_HVM
  *  - 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_GUEST
+ *  - SPEC_CTRL_EXIT_TO_PV
+ *  - SPEC_CTRL_EXIT_TO_HVM
  */
 
 .macro DO_OVERWRITE_RSB tmp=rax
@@ -117,7 +120,7 @@
     mov %\tmp, %rsp                 /* Restore old %rsp */
 .endm
 
-.macro DO_SPEC_CTRL_ENTRY_FROM_VMEXIT
+.macro DO_SPEC_CTRL_ENTRY_FROM_HVM
 /*
  * Requires %rbx=current, %rsp=regs/cpuinfo
  * Clobbers %rax, %rcx, %rdx
@@ -216,23 +219,23 @@
 .endm
 
 /* Use after a VMEXIT from an HVM guest. */
-#define SPEC_CTRL_ENTRY_FROM_VMEXIT                                     \
+#define SPEC_CTRL_ENTRY_FROM_HVM                                        \
     ALTERNATIVE __stringify(ASM_NOP40),                                 \
-        DO_OVERWRITE_RSB, X86_FEATURE_RSB_VMEXIT;                       \
+        DO_OVERWRITE_RSB, X86_FEATURE_SC_RSB_HVM;                       \
     ALTERNATIVE __stringify(ASM_NOP36),                                 \
-        DO_SPEC_CTRL_ENTRY_FROM_VMEXIT, X86_FEATURE_SC_MSR
+        DO_SPEC_CTRL_ENTRY_FROM_HVM, X86_FEATURE_SC_MSR
 
 /* Use after an entry from PV context (syscall/sysenter/int80/int82/etc). */
 #define SPEC_CTRL_ENTRY_FROM_PV                                         \
     ALTERNATIVE __stringify(ASM_NOP40),                                 \
-        DO_OVERWRITE_RSB, X86_FEATURE_RSB_NATIVE;                       \
+        DO_OVERWRITE_RSB, X86_FEATURE_SC_RSB_PV;                        \
     ALTERNATIVE __stringify(ASM_NOP25),                                 \
         __stringify(DO_SPEC_CTRL_ENTRY maybexen=0), X86_FEATURE_SC_MSR
 
 /* Use in interrupt/exception context.  May interrupt Xen or PV context. */
 #define SPEC_CTRL_ENTRY_FROM_INTR                                       \
     ALTERNATIVE __stringify(ASM_NOP40),                                 \
-        DO_OVERWRITE_RSB, X86_FEATURE_RSB_NATIVE;                       \
+        DO_OVERWRITE_RSB, X86_FEATURE_SC_RSB_PV;                        \
     ALTERNATIVE __stringify(ASM_NOP33),                                 \
         __stringify(DO_SPEC_CTRL_ENTRY maybexen=1), X86_FEATURE_SC_MSR
 
@@ -241,12 +244,22 @@
     ALTERNATIVE __stringify(ASM_NOP17),                                 \
         DO_SPEC_CTRL_EXIT_TO_XEN, X86_FEATURE_SC_MSR
 
-/* Use when exiting to guest context. */
-#define SPEC_CTRL_EXIT_TO_GUEST                                         \
+/* Use when exiting to PV guest context. */
+#define SPEC_CTRL_EXIT_TO_PV                                            \
     ALTERNATIVE __stringify(ASM_NOP24),                                 \
         DO_SPEC_CTRL_EXIT_TO_GUEST, X86_FEATURE_SC_MSR
 
-/* TODO: Drop these when the alternatives infrastructure is NMI/#MC safe. */
+/* Use when exiting to HVM guest context. */
+#define SPEC_CTRL_EXIT_TO_HVM                                           \
+    ALTERNATIVE __stringify(ASM_NOP24),                                 \
+        DO_SPEC_CTRL_EXIT_TO_GUEST, X86_FEATURE_SC_MSR
+
+/*
+ * Use in IST interrupt/exception context.  May interrupt Xen or PV context.
+ * Fine grain control of SCF_ist_wrmsr is needed for safety in the S3 resume
+ * path to avoid using MSR_SPEC_CTRL before the microcode introducing it has
+ * been reloaded.
+ */
 .macro SPEC_CTRL_ENTRY_FROM_INTR_IST
 /*
  * Requires %rsp=regs, %r14=stack_end
@@ -293,6 +306,7 @@ UNLIKELY_DISPATCH_LABEL(\@_serialise):
     UNLIKELY_END(\@_serialise)
 .endm
 
+/* Use when exiting to Xen in IST context. */
 .macro SPEC_CTRL_EXIT_TO_XEN_IST
 /*
  * Requires %rbx=stack_end
