linux-kernel - [RFC v2 13/32] x86/io: Allow to override inX() and outX() implementation

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Date:   Mon, 26 Apr 2021 11:01:40 -0700
From:   Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Tony Luck <tony.luck@...el.com>
Cc:     Andi Kleen <ak@...ux.intel.com>,
        Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        Raj Ashok <ashok.raj@...el.com>,
        Sean Christopherson <seanjc@...gle.com>,
        linux-kernel@...r.kernel.org,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
Subject: [RFC v2 13/32] x86/io: Allow to override inX() and outX() implementation

From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>

The patch allows to override the implementation of the port IO
helpers. TDX code will provide an implementation that redirect the
helpers to paravirt calls.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Reviewed-by: Andi Kleen <ak@...ux.intel.com>
Reviewed-by: Tony Luck <tony.luck@...el.com>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
---
 arch/x86/include/asm/io.h | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
index d726459d08e5..ef7a686a55a9 100644
--- a/arch/x86/include/asm/io.h
+++ b/arch/x86/include/asm/io.h
@@ -271,18 +271,26 @@ static inline bool sev_key_active(void) { return false; }
 
 #endif /* CONFIG_AMD_MEM_ENCRYPT */
 
+#ifndef __out
+#define __out(bwl, bw)							\
+	asm volatile("out" #bwl " %" #bw "0, %w1" : : "a"(value), "Nd"(port))
+#endif
+
+#ifndef __in
+#define __in(bwl, bw)							\
+	asm volatile("in" #bwl " %w1, %" #bw "0" : "=a"(value) : "Nd"(port))
+#endif
+
 #define BUILDIO(bwl, bw, type)						\
 static inline void out##bwl(unsigned type value, int port)		\
 {									\
-	asm volatile("out" #bwl " %" #bw "0, %w1"			\
-		     : : "a"(value), "Nd"(port));			\
+	__out(bwl, bw);							\
 }									\
 									\
 static inline unsigned type in##bwl(int port)				\
 {									\
 	unsigned type value;						\
-	asm volatile("in" #bwl " %w1, %" #bw "0"			\
-		     : "=a"(value) : "Nd"(port));			\
+	__in(bwl, bw);							\
 	return value;							\
 }									\
 									\
-- 
2.25.1