1 files changed, 66 insertions, 0 deletions
diff --git a/arch/x86/include/asm/gsseg.h b/arch/x86/include/asm/gsseg.h
new file mode 100644
index 000000000000..ab6a595cea70
--- /dev/null
+++ b/arch/x86/include/asm/gsseg.h
@@ -0,0 +1,66 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef _ASM_X86_GSSEG_H
+#define _ASM_X86_GSSEG_H
+
+#include <linux/types.h>
+
+#include <asm/asm.h>
+#include <asm/cpufeature.h>
+#include <asm/alternative.h>
+#include <asm/processor.h>
+#include <asm/nops.h>
+
+#ifdef CONFIG_X86_64
+
+extern asmlinkage void asm_load_gs_index(u16 selector);
+
+/* Replace with "lkgs %di" once binutils support LKGS instruction */
+#define LKGS_DI _ASM_BYTES(0xf2,0x0f,0x00,0xf7)
+
+static inline void native_lkgs(unsigned int selector)
+{
+	u16 sel = selector;
+	asm_inline volatile("1: " LKGS_DI
+			    _ASM_EXTABLE_TYPE_REG(1b, 1b, EX_TYPE_ZERO_REG, %k[sel])
+			    : [sel] "+D" (sel));
+}
+
+static inline void native_load_gs_index(unsigned int selector)
+{
+	if (cpu_feature_enabled(X86_FEATURE_LKGS)) {
+		native_lkgs(selector);
+	} else {
+		unsigned long flags;
+
+		local_irq_save(flags);
+		asm_load_gs_index(selector);
+		local_irq_restore(flags);
+	}
+}
+
+#endif /* CONFIG_X86_64 */
+
+static inline void __init lkgs_init(void)
+{
+#ifdef CONFIG_PARAVIRT_XXL
+#ifdef CONFIG_X86_64
+	if (cpu_feature_enabled(X86_FEATURE_LKGS))
+		pv_ops.cpu.load_gs_index = native_lkgs;
+#endif
+#endif
+}
+
+#ifndef CONFIG_PARAVIRT_XXL
+
+static inline void load_gs_index(unsigned int selector)
+{
+#ifdef CONFIG_X86_64
+	native_load_gs_index(selector);
+#else
+	loadsegment(gs, selector);
+#endif
+}
+
+#endif /* CONFIG_PARAVIRT_XXL */
+
+#endif /* _ASM_X86_GSSEG_H */