4 files changed, 158 insertions, 0 deletions

diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
index 07c31899c9c2..9e609206fac9 100644
--- a/arch/x86/lib/Makefile
+++ b/arch/x86/lib/Makefile
@@ -9,6 +9,8 @@ lib-y += thunk_$(BITS).o
 lib-y += usercopy_$(BITS).o getuser.o putuser.o
 lib-y += memcpy_$(BITS).o
 
+obj-y += msr-reg.o msr-reg-export.o
+
 ifeq ($(CONFIG_X86_32),y)
         obj-y += atomic64_32.o
         lib-y += checksum_32.o
diff --git a/arch/x86/lib/msr-reg-export.c b/arch/x86/lib/msr-reg-export.c
new file mode 100644
index 000000000000..a311cc59b65d
--- /dev/null
+++ b/arch/x86/lib/msr-reg-export.c
@@ -0,0 +1,5 @@
+#include <linux/module.h>
+#include <asm/msr.h>
+
+EXPORT_SYMBOL(native_rdmsr_safe_regs);
+EXPORT_SYMBOL(native_wrmsr_safe_regs);
diff --git a/arch/x86/lib/msr-reg.S b/arch/x86/lib/msr-reg.S
new file mode 100644
index 000000000000..69fa10623f21
--- /dev/null
+++ b/arch/x86/lib/msr-reg.S
@@ -0,0 +1,102 @@
+#include <linux/linkage.h>
+#include <linux/errno.h>
+#include <asm/dwarf2.h>
+#include <asm/asm.h>
+#include <asm/msr.h>
+
+#ifdef CONFIG_X86_64
+/*
+ * int native_{rdmsr,wrmsr}_safe_regs(u32 gprs[8]);
+ *
+ * reg layout: u32 gprs[eax, ecx, edx, ebx, esp, ebp, esi, edi]
+ *
+ */
+.macro op_safe_regs op
+ENTRY(native_\op\()_safe_regs)
+        CFI_STARTPROC
+        pushq_cfi %rbx
+        pushq_cfi %rbp
+        movq    %rdi, %r10      /* Save pointer */
+        xorl    %r11d, %r11d    /* Return value */
+        movl    (%rdi), %eax
+        movl    4(%rdi), %ecx
+        movl    8(%rdi), %edx
+        movl    12(%rdi), %ebx
+        movl    20(%rdi), %ebp
+        movl    24(%rdi), %esi
+        movl    28(%rdi), %edi
+        CFI_REMEMBER_STATE
+1:      \op
+2:      movl    %eax, (%r10)
+        movl    %r11d, %eax     /* Return value */
+        movl    %ecx, 4(%r10)
+        movl    %edx, 8(%r10)
+        movl    %ebx, 12(%r10)
+        movl    %ebp, 20(%r10)
+        movl    %esi, 24(%r10)
+        movl    %edi, 28(%r10)
+        popq_cfi %rbp
+        popq_cfi %rbx
+        ret
+3:
+        CFI_RESTORE_STATE
+        movl    $-EIO, %r11d
+        jmp     2b
+
+        _ASM_EXTABLE(1b, 3b)
+        CFI_ENDPROC
+ENDPROC(native_\op\()_safe_regs)
+.endm
+
+#else /* X86_32 */
+
+.macro op_safe_regs op
+ENTRY(native_\op\()_safe_regs)
+        CFI_STARTPROC
+        pushl_cfi %ebx
+        pushl_cfi %ebp
+        pushl_cfi %esi
+        pushl_cfi %edi
+        pushl_cfi $0              /* Return value */
+        pushl_cfi %eax
+        movl    4(%eax), %ecx
+        movl    8(%eax), %edx
+        movl    12(%eax), %ebx
+        movl    20(%eax), %ebp
+        movl    24(%eax), %esi
+        movl    28(%eax), %edi
+        movl    (%eax), %eax
+        CFI_REMEMBER_STATE
+1:      \op
+2:      pushl_cfi %eax
+        movl    4(%esp), %eax
+        popl_cfi (%eax)
+        addl    $4, %esp
+        CFI_ADJUST_CFA_OFFSET -4
+        movl    %ecx, 4(%eax)
+        movl    %edx, 8(%eax)
+        movl    %ebx, 12(%eax)
+        movl    %ebp, 20(%eax)
+        movl    %esi, 24(%eax)
+        movl    %edi, 28(%eax)
+        popl_cfi %eax
+        popl_cfi %edi
+        popl_cfi %esi
+        popl_cfi %ebp
+        popl_cfi %ebx
+        ret
+3:
+        CFI_RESTORE_STATE
+        movl    $-EIO, 4(%esp)
+        jmp     2b
+
+        _ASM_EXTABLE(1b, 3b)
+        CFI_ENDPROC
+ENDPROC(native_\op\()_safe_regs)
+.endm
+
+#endif
+
+op_safe_regs rdmsr
+op_safe_regs wrmsr
+
diff --git a/arch/x86/lib/msr.c b/arch/x86/lib/msr.c
index caa24aca8115..33a1e3ca22d8 100644
--- a/arch/x86/lib/msr.c
+++ b/arch/x86/lib/msr.c
@@ -175,3 +175,52 @@ int wrmsr_safe_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h)
         return err ? err : rv.err;
 }
 EXPORT_SYMBOL(wrmsr_safe_on_cpu);
+
+/*
+ * These variants are significantly slower, but allows control over
+ * the entire 32-bit GPR set.
+ */
+struct msr_regs_info {
+        u32 *regs;
+        int err;
+};
+
+static void __rdmsr_safe_regs_on_cpu(void *info)
+{
+        struct msr_regs_info *rv = info;
+
+        rv->err = rdmsr_safe_regs(rv->regs);
+}
+
+static void __wrmsr_safe_regs_on_cpu(void *info)
+{
+        struct msr_regs_info *rv = info;
+
+        rv->err = wrmsr_safe_regs(rv->regs);
+}
+
+int rdmsr_safe_regs_on_cpu(unsigned int cpu, u32 *regs)
+{
+        int err;
+        struct msr_regs_info rv;
+
+        rv.regs   = regs;
+        rv.err    = -EIO;
+        err = smp_call_function_single(cpu, __rdmsr_safe_regs_on_cpu, &rv, 1);
+
+        return err ? err : rv.err;
+}
+EXPORT_SYMBOL(rdmsr_safe_regs_on_cpu);
+
+int wrmsr_safe_regs_on_cpu(unsigned int cpu, u32 *regs)
+{
+        int err;
+        struct msr_regs_info rv;
+
+        rv.regs = regs;
+        rv.err  = -EIO;
+        err = smp_call_function_single(cpu, __wrmsr_safe_regs_on_cpu, &rv, 1);
+
+        return err ? err : rv.err;
+}
+EXPORT_SYMBOL(wrmsr_safe_regs_on_cpu);