x86/spec_ctrl: Split X86_FEATURE_SC_MSR into PV and HVM variants

In order to separately control whether MSR_SPEC_CTRL is virtualised for PV and
HVM guests, split the feature used to control runtime alternatives into two.
Xen will use MSR_SPEC_CTRL itself if either of these features are active.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
master commit: fa9eb09d446a1279f5e861e6b84fa8675dabf148
master date: 2018-05-16 12:19:10 +0100

diff --git a/xen/arch/x86/cpu/common.c b/xen/arch/x86/cpu/common.c
index 15e831abde39fb7c79b442c803b888de8290747f..0e8fd2e74db84e6d83b20c45d8dc3af1f76ca172 100644 (file)
--- a/xen/arch/x86/cpu/common.c
+++ b/xen/arch/x86/cpu/common.c
@@ -359,9 +359,12 @@ void __cpuinit identify_cpu(struct cpuinfo_x86 *c)
                if (test_bit(X86_FEATURE_IND_THUNK_JMP,
                             boot_cpu_data.x86_capability))
                        __set_bit(X86_FEATURE_IND_THUNK_JMP, c->x86_capability);
-               if (test_bit(X86_FEATURE_SC_MSR,
+               if (test_bit(X86_FEATURE_SC_MSR_PV,
                             boot_cpu_data.x86_capability))
-                       __set_bit(X86_FEATURE_SC_MSR, c->x86_capability);
+                       __set_bit(X86_FEATURE_SC_MSR_PV, c->x86_capability);
+               if (test_bit(X86_FEATURE_SC_MSR_HVM,
+                            boot_cpu_data.x86_capability))
+                       __set_bit(X86_FEATURE_SC_MSR_HVM, c->x86_capability);
                if (test_bit(X86_FEATURE_SC_RSB_PV,
                             boot_cpu_data.x86_capability))
                        __set_bit(X86_FEATURE_SC_RSB_PV, c->x86_capability);

diff --git a/xen/arch/x86/spec_ctrl.c b/xen/arch/x86/spec_ctrl.c
index 778f8e58331dd7f787f8d74bf34b2a572cd6e280..fece1056b9b34682958b1bd0ca89afca14c2a888 100644 (file)
--- a/xen/arch/x86/spec_ctrl.c
+++ b/xen/arch/x86/spec_ctrl.c
@@ -114,7 +114,8 @@ static void __init print_details(enum ind_thunk thunk, uint64_t caps)
            thunk == THUNK_RETPOLINE ? "RETPOLINE" :
            thunk == THUNK_LFENCE    ? "LFENCE" :
            thunk == THUNK_JMP       ? "JMP" : "?",
-           boot_cpu_has(X86_FEATURE_SC_MSR) ?
+           (boot_cpu_has(X86_FEATURE_SC_MSR_PV) ||
+            boot_cpu_has(X86_FEATURE_SC_MSR_HVM)) ?
            default_xen_spec_ctrl & SPEC_CTRL_IBRS    ? " IBRS+" :
                                                        " IBRS-"      : "",
            opt_ibpb                                  ? " IBPB"       : "",
@@ -283,7 +284,8 @@ void __init init_speculation_mitigations(void)
          * need the IBRS entry/exit logic to virtualise IBRS support for
          * guests.
          */
-        __set_bit(X86_FEATURE_SC_MSR, boot_cpu_data.x86_capability);
+        __set_bit(X86_FEATURE_SC_MSR_PV, boot_cpu_data.x86_capability);
+        __set_bit(X86_FEATURE_SC_MSR_HVM, boot_cpu_data.x86_capability);
 
         if ( ibrs )
             default_xen_spec_ctrl |= SPEC_CTRL_IBRS;

diff --git a/xen/include/asm-x86/cpufeature.h b/xen/include/asm-x86/cpufeature.h
index d1409827086dccf376f94e6d8e7a5b641066dafd..3aaa6c8078e82e174bd649df8c1eecf1dbab9d69 100644 (file)
--- a/xen/include/asm-x86/cpufeature.h
+++ b/xen/include/asm-x86/cpufeature.h
@@ -65,7 +65,8 @@
 #define X86_FEATURE_IND_THUNK_LFENCE (3*32+ 1) /* Use IND_THUNK_LFENCE */
 #define X86_FEATURE_IND_THUNK_JMP   (3*32+ 2) /* Use IND_THUNK_JMP */
 #define X86_FEATURE_XEN_IBPB        (3*32+ 3) /* IBRSB || IBPB */
-#define X86_FEATURE_SC_MSR          (3*32+ 4) /* MSR_SPEC_CTRL used by Xen */
+#define X86_FEATURE_SC_MSR_PV       (3*32+ 4) /* MSR_SPEC_CTRL used by Xen for PV */
+#define X86_FEATURE_SC_MSR_HVM      (3*32+ 5) /* MSR_SPEC_CTRL used by Xen for HVM */
 #define X86_FEATURE_SC_RSB_PV       (3*32+ 6) /* RSB overwrite needed for PV */
 #define X86_FEATURE_SC_RSB_HVM      (3*32+ 7) /* RSB overwrite needed for HVM */
 #define X86_FEATURE_CONSTANT_TSC (3*32+ 8) /* TSC ticks at a constant rate */
@@ -76,7 +77,7 @@
 #define X86_FEATURE_XTOPOLOGY    (3*32+13) /* cpu topology enum extensions */
 #define X86_FEATURE_CPUID_FAULTING (3*32+14) /* cpuid faulting */
 #define X86_FEATURE_CLFLUSH_MONITOR (3*32+15) /* clflush reqd with monitor */
-#define X86_FEATURE_SC_MSR_IDLE     (3*32+16) /* SC_MSR && default_xen_spec_ctrl */
+#define X86_FEATURE_SC_MSR_IDLE     (3*32+16) /* (SC_MSR_PV || SC_MSR_HVM) && default_xen_spec_ctrl */
 
 /* Intel-defined CPU features, CPUID level 0x00000001 (ecx), word 4 */
 #define X86_FEATURE_XMM3       (4*32+ 0) /* Streaming SIMD Extensions-3 */

diff --git a/xen/include/asm-x86/spec_ctrl_asm.h b/xen/include/asm-x86/spec_ctrl_asm.h
index be5cba318e14e6cd706afdc11b013952043aa32c..30077d71fbf146b307c1ff43e9202ad5fc5dcee2 100644 (file)
--- a/xen/include/asm-x86/spec_ctrl_asm.h
+++ b/xen/include/asm-x86/spec_ctrl_asm.h
@@ -223,36 +223,36 @@
     ALTERNATIVE __stringify(ASM_NOP40),                                 \
         DO_OVERWRITE_RSB, X86_FEATURE_SC_RSB_HVM;                       \
     ALTERNATIVE __stringify(ASM_NOP33),                                 \
-        DO_SPEC_CTRL_ENTRY_FROM_HVM, X86_FEATURE_SC_MSR
+        DO_SPEC_CTRL_ENTRY_FROM_HVM, X86_FEATURE_SC_MSR_HVM
 
 /* 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_SC_RSB_PV;                        \
     ALTERNATIVE __stringify(ASM_NOP25),                                 \
-        __stringify(DO_SPEC_CTRL_ENTRY maybexen=0), X86_FEATURE_SC_MSR
+        __stringify(DO_SPEC_CTRL_ENTRY maybexen=0), X86_FEATURE_SC_MSR_PV
 
 /* 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_SC_RSB_PV;                        \
     ALTERNATIVE __stringify(ASM_NOP39),                                 \
-        __stringify(DO_SPEC_CTRL_ENTRY maybexen=1), X86_FEATURE_SC_MSR
+        __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 __stringify(ASM_NOP23),                                 \
-        DO_SPEC_CTRL_EXIT_TO_XEN, X86_FEATURE_SC_MSR
+        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 __stringify(ASM_NOP24),                                 \
-        DO_SPEC_CTRL_EXIT_TO_GUEST, X86_FEATURE_SC_MSR
+        DO_SPEC_CTRL_EXIT_TO_GUEST, X86_FEATURE_SC_MSR_PV
 
 /* 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
+        DO_SPEC_CTRL_EXIT_TO_GUEST, X86_FEATURE_SC_MSR_HVM
 
 /*
  * Use in IST interrupt/exception context.  May interrupt Xen or PV context.