@@ -1226,4 +1226,10 @@
* a #GP
*/
+/* Instruction opcode for WRMSRNS supported in binutils >= 2.40 */
+#define ASM_WRMSRNS _ASM_BYTES(0x0f,0x01,0xc6)
+
+/* Instruction opcode for the immediate form RDMSR/WRMSRNS */
+#define ASM_WRMSRNS_RAX _ASM_BYTES(0xc4,0xe7,0x7a,0xf6,0xc0)
+
#endif /* _ASM_X86_MSR_INDEX_H */
@@ -64,6 +64,29 @@
RET
.endm
+/*
+ * Write EAX to MSR_IA32_SPEC_CTRL.
+ *
+ * Choose the best WRMSR instruction based on availability.
+ *
+ * Replace with 'wrmsrns' and 'wrmsrns %rax, $MSR_IA32_SPEC_CTRL' once binutils support them.
+ */
+.macro WRITE_EAX_TO_MSR_IA32_SPEC_CTRL
+ ALTERNATIVE_2 __stringify(mov $MSR_IA32_SPEC_CTRL, %ecx; \
+ xor %edx, %edx; \
+ mov %edi, %eax; \
+ ds wrmsr), \
+ __stringify(mov $MSR_IA32_SPEC_CTRL, %ecx; \
+ xor %edx, %edx; \
+ mov %edi, %eax; \
+ ASM_WRMSRNS), \
+ X86_FEATURE_WRMSRNS, \
+ __stringify(xor %_ASM_AX, %_ASM_AX; \
+ mov %edi, %eax; \
+ ASM_WRMSRNS_RAX; .long MSR_IA32_SPEC_CTRL), \
+ X86_FEATURE_MSR_IMM
+.endm
+
.section .noinstr.text, "ax"
/**
@@ -123,10 +146,7 @@ SYM_FUNC_START(__vmx_vcpu_run)
movl PER_CPU_VAR(x86_spec_ctrl_current), %esi
cmp %edi, %esi
je .Lspec_ctrl_done
- mov $MSR_IA32_SPEC_CTRL, %ecx
- xor %edx, %edx
- mov %edi, %eax
- wrmsr
+ WRITE_EAX_TO_MSR_IA32_SPEC_CTRL
.Lspec_ctrl_done:
Signed-off-by: Xin Li (Intel) <xin@zytor.com> --- arch/x86/include/asm/msr-index.h | 6 ++++++ arch/x86/kvm/vmx/vmenter.S | 28 ++++++++++++++++++++++++---- 2 files changed, 30 insertions(+), 4 deletions(-)