From 9e90199c25aec31b4509213881511948f6c763c8 Mon Sep 17 00:00:00 2001
From: Xiao Guangrong <guangrong.xiao@linux.intel.com>
Date: Tue, 22 Mar 2016 16:51:17 +0800
Subject: x86: pkey: introduce write_pkru() for KVM

KVM will use it to switch pkru between guest and host.

CC: Ingo Molnar <mingo@redhat.com>
CC: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Xiao Guangrong <guangrong.xiao@linux.intel.com>
Signed-off-by: Huaitong Han <huaitong.han@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 arch/x86/include/asm/special_insns.h | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

(limited to 'arch/x86/include/asm/special_insns.h')

diff --git a/arch/x86/include/asm/special_insns.h b/arch/x86/include/asm/special_insns.h
index aee6e76e561ec..d96d043777656 100644
--- a/arch/x86/include/asm/special_insns.h
+++ b/arch/x86/include/asm/special_insns.h
@@ -113,11 +113,27 @@ static inline u32 __read_pkru(void)
 		     : "c" (ecx));
 	return pkru;
 }
+
+static inline void __write_pkru(u32 pkru)
+{
+	u32 ecx = 0, edx = 0;
+
+	/*
+	 * "wrpkru" instruction.  Loads contents in EAX to PKRU,
+	 * requires that ecx = edx = 0.
+	 */
+	asm volatile(".byte 0x0f,0x01,0xef\n\t"
+		     : : "a" (pkru), "c"(ecx), "d"(edx));
+}
 #else
 static inline u32 __read_pkru(void)
 {
 	return 0;
 }
+
+static inline void __write_pkru(u32 pkru)
+{
+}
 #endif
 
 static inline void native_wbinvd(void)
-- 
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