linux-kernel - [PATCH 3.16 031/131] x86/cpu: Make alternative_msr

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Message-ID: <lsq.1538257387.550512017@decadent.org.uk>
Date:   Sat, 29 Sep 2018 22:43:07 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Linus Torvalds" <torvalds@...ux-foundation.org>,
        "Konrad Rzeszutek Wilk" <konrad.wilk@...cle.com>,
        "David Woodhouse" <dwmw@...zon.co.uk>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        "Jim Mattson" <jmattson@...gle.com>
Subject: [PATCH 3.16 031/131] x86/cpu: Make alternative_msr_write work for
 32-bit code

3.16.59-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Jim Mattson <jmattson@...gle.com>

commit 5f2b745f5e1304f438f9b2cd03ebc8120b6e0d3b upstream.

Cast val and (val >> 32) to (u32), so that they fit in a
general-purpose register in both 32-bit and 64-bit code.

[ tglx: Made it u32 instead of uintptr_t ]

Fixes: c65732e4f721 ("x86/cpu: Restore CPUID_8000_0008_EBX reload")
Signed-off-by: Jim Mattson <jmattson@...gle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Acked-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: David Woodhouse <dwmw@...zon.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/x86/include/asm/nospec-branch.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -219,8 +219,8 @@ void alternative_msr_write(unsigned int
 {
 	asm volatile(ALTERNATIVE("", "wrmsr", %c[feature])
 		: : "c" (msr),
-		    "a" (val),
-		    "d" (val >> 32),
+		    "a" ((u32)val),
+		    "d" ((u32)(val >> 32)),
 		    [feature] "i" (feature)
 		: "memory");
 }