linux-kernel - [PATCH 2/6] x86/alternative: Add alternative_io

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Message-Id: <1415731396-19364-3-git-send-email-ross.zwisler@linux.intel.com>
Date:	Tue, 11 Nov 2014 11:43:12 -0700
From:	Ross Zwisler <ross.zwisler@...ux.intel.com>
To:	linux-kernel@...r.kernel.org
Cc:	Ross Zwisler <ross.zwisler@...ux.intel.com>,
	H Peter Anvin <h.peter.anvin@...el.com>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	David Airlie <airlied@...ux.ie>,
	dri-devel@...ts.freedesktop.org, x86@...nel.org
Subject: [PATCH 2/6] x86/alternative: Add alternative_io_2

Add alternative_io_2 in the spirit of alternative_input_2 and
alternative_io.  This will allow us to have instructions with an output
parameter that vary based on two CPU features.

Signed-off-by: Ross Zwisler <ross.zwisler@...ux.intel.com>
Cc: H Peter Anvin <h.peter.anvin@...el.com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: David Airlie <airlied@...ux.ie>
Cc: dri-devel@...ts.freedesktop.org
Cc: x86@...nel.org
---
 arch/x86/include/asm/alternative.h | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index 473bdbe..7d9ead9 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -180,6 +180,20 @@ static inline int alternatives_text_reserved(void *start, void *end)
 	asm volatile (ALTERNATIVE(oldinstr, newinstr, feature)		\
 		: output : "i" (0), ## input)
 
+/*
+ * This is similar to alternative_io. But it has two features and
+ * respective instructions.
+ *
+ * If CPU has feature2, newinstr2 is used.
+ * Otherwise, if CPU has feature1, newinstr1 is used.
+ * Otherwise, oldinstr is used.
+ */
+#define alternative_io_2(oldinstr, newinstr1, feature1, newinstr2,	     \
+			   feature2, output, input...)			     \
+	asm volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1,	     \
+		newinstr2, feature2)					     \
+		: output : "i" (0), ## input)
+
 /* Like alternative_io, but for replacing a direct call with another one. */
 #define alternative_call(oldfunc, newfunc, feature, output, input...)	\
 	asm volatile (ALTERNATIVE("call %P[old]", "call %P[new]", feature) \
-- 
1.9.3

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