x86/mm: Avoid redundant interrupt disable in load_mm_cr4()

load_mm_cr4() is always called with interrupts disabled from:

 - switch_mm_irqs_off()
 - refresh_pce(), which is a on_each_cpu() callback

Thus, disabling interrupts in cr4_set/clear_bits() is redundant.

Implement cr4_set/clear_bits_irqsoff() helpers, rename load_mm_cr4() to
load_mm_cr4_irqsoff() and use the new helpers. The new helpers do not need
a lockdep assert as __cr4_set() has one already.

The renaming in combination with the checks in __cr4_set() ensure that any
changes in the boundary conditions at the call sites will be detected.

[ tglx: Massaged change log ]

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/0fbbcb64-5f26-4ffb-1bb9-4f5f48426893@siemens.com

1 files changed, 23 insertions, 7 deletions

diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
index dee375831962..6f66d841262d 100644
--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -290,26 +290,42 @@ static inline void __cr4_set(unsigned long cr4)
 }
 
 /* Set in this cpu's CR4. */
-static inline void cr4_set_bits(unsigned long mask)
+static inline void cr4_set_bits_irqsoff(unsigned long mask)
 {
-	unsigned long cr4, flags;
+	unsigned long cr4;
 
-	local_irq_save(flags);
 	cr4 = this_cpu_read(cpu_tlbstate.cr4);
 	if ((cr4 | mask) != cr4)
 		__cr4_set(cr4 | mask);
-	local_irq_restore(flags);
 }
 
 /* Clear in this cpu's CR4. */
-static inline void cr4_clear_bits(unsigned long mask)
+static inline void cr4_clear_bits_irqsoff(unsigned long mask)
 {
-	unsigned long cr4, flags;
+	unsigned long cr4;
 
-	local_irq_save(flags);
 	cr4 = this_cpu_read(cpu_tlbstate.cr4);
 	if ((cr4 & ~mask) != cr4)
 		__cr4_set(cr4 & ~mask);
+}
+
+/* Set in this cpu's CR4. */
+static inline void cr4_set_bits(unsigned long mask)
+{
+	unsigned long flags;
+
+	local_irq_save(flags);
+	cr4_set_bits_irqsoff(mask);
+	local_irq_restore(flags);
+}
+
+/* Clear in this cpu's CR4. */
+static inline void cr4_clear_bits(unsigned long mask)
+{
+	unsigned long flags;
+
+	local_irq_save(flags);
+	cr4_clear_bits_irqsoff(mask);
 	local_irq_restore(flags);
 }