linux-kernel - [PATCH v2 1/2] x86: refactor CR4 setting and shadow write

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Date:   Fri, 24 Nov 2017 19:29:06 -0800
From:   Nadav Amit <namit@...are.com>
To:     <linux-kernel@...r.kernel.org>, <linux-edac@...r.kernel.org>
CC:     <nadav.amit@...il.com>, Nadav Amit <namit@...are.com>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, <x86@...nel.org>
Subject: [PATCH v2 1/2] x86: refactor CR4 setting and shadow write

Refactor the write to CR4 and its shadow value. This is done in
preparation for the addition of an assertion to check that IRQs are
disabled during CR4 update.

No functional change.

Cc: Andy Lutomirski <luto@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: x86@...nel.org

Signed-off-by: Nadav Amit <namit@...are.com>
---
 arch/x86/include/asm/tlbflush.h | 24 +++++++++++-------------
 1 file changed, 11 insertions(+), 13 deletions(-)

diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
index 509046cfa5ce..e736f7f0ba92 100644
--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -173,17 +173,20 @@ static inline void cr4_init_shadow(void)
 	this_cpu_write(cpu_tlbstate.cr4, __read_cr4());
 }
 
+static inline void __cr4_set(unsigned long cr4)
+{
+	this_cpu_write(cpu_tlbstate.cr4, cr4);
+	__write_cr4(cr4);
+}
+
 /* Set in this cpu's CR4. */
 static inline void cr4_set_bits(unsigned long mask)
 {
 	unsigned long cr4;
 
 	cr4 = this_cpu_read(cpu_tlbstate.cr4);
-	if ((cr4 | mask) != cr4) {
-		cr4 |= mask;
-		this_cpu_write(cpu_tlbstate.cr4, cr4);
-		__write_cr4(cr4);
-	}
+	if ((cr4 | mask) != cr4)
+		__cr4_set(cr4 | mask);
 }
 
 /* Clear in this cpu's CR4. */
@@ -192,11 +195,8 @@ static inline void cr4_clear_bits(unsigned long mask)
 	unsigned long cr4;
 
 	cr4 = this_cpu_read(cpu_tlbstate.cr4);
-	if ((cr4 & ~mask) != cr4) {
-		cr4 &= ~mask;
-		this_cpu_write(cpu_tlbstate.cr4, cr4);
-		__write_cr4(cr4);
-	}
+	if ((cr4 & ~mask) != cr4)
+		__cr4_set(cr4 & ~mask);
 }
 
 static inline void cr4_toggle_bits(unsigned long mask)
@@ -204,9 +204,7 @@ static inline void cr4_toggle_bits(unsigned long mask)
 	unsigned long cr4;
 
 	cr4 = this_cpu_read(cpu_tlbstate.cr4);
-	cr4 ^= mask;
-	this_cpu_write(cpu_tlbstate.cr4, cr4);
-	__write_cr4(cr4);
+	__cr4_set(cr4 ^ mask);
 }
 
 /* Read the CR4 shadow. */
-- 
2.14.1