linux-kernel - [PATCH 03/16] x86/microcode: Convert to bare minimum MSR accessors

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Message-Id: <20170120202955.4091-4-bp@alien8.de>
Date:   Fri, 20 Jan 2017 21:29:42 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     X86 ML <x86@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH 03/16] x86/microcode: Convert to bare minimum MSR accessors

From: Borislav Petkov <bp@...e.de>

Having tracepoints to the MSR accessors makes them unsuitable for early
microcode loading: think 32-bit before paging is enabled and us chasing
pointers to test whether a tracepoint is enabled or not. Results in a
reliable triple fault.

Convert to the bare ones.

Signed-off-by: Borislav Petkov <bp@...e.de>
---
 arch/x86/include/asm/microcode.h | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/microcode.h b/arch/x86/include/asm/microcode.h
index 38711df3bcb5..90b22bbdfce9 100644
--- a/arch/x86/include/asm/microcode.h
+++ b/arch/x86/include/asm/microcode.h
@@ -7,18 +7,17 @@
 
 #define native_rdmsr(msr, val1, val2)			\
 do {							\
-	u64 __val = native_read_msr((msr));		\
+	u64 __val = __rdmsr((msr));			\
 	(void)((val1) = (u32)__val);			\
 	(void)((val2) = (u32)(__val >> 32));		\
 } while (0)
 
 #define native_wrmsr(msr, low, high)			\
-	native_write_msr(msr, low, high)
+	__wrmsr(msr, low, high)
 
 #define native_wrmsrl(msr, val)				\
-	native_write_msr((msr),				\
-			 (u32)((u64)(val)),		\
-			 (u32)((u64)(val) >> 32))
+	__wrmsr((msr), (u32)((u64)(val)),		\
+		       (u32)((u64)(val) >> 32))
 
 struct ucode_patch {
 	struct list_head plist;
-- 
2.11.0