x86/apic: Add apic->eoi_write() callback

Add eoi_write callback so that kvm can override
eoi accesses without touching the rest of the apic.
As a side-effect, this will enable a micro-optimization
for apics using msr.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Cc: Avi Kivity <avi@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: gleb@redhat.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/0df425d746c49ac2ecc405174df87752869629d2.1337184153.git.mst@redhat.com
[ tidied it up a bit ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 15 insertions, 1 deletions

diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index a09e9ab0bbdf..bf8d065dd977 100644
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -351,6 +351,14 @@ struct apic {
         /* apic ops */
         u32 (*read)(u32 reg);
         void (*write)(u32 reg, u32 v);
+        /*
+         * ->eoi_write() has the same signature as ->write().
+         *
+         * Drivers can support both ->eoi_write() and ->write() by passing the same
+         * callback value. Kernel can override ->eoi_write() and fall back
+         * on write for EOI.
+         */
+        void (*eoi_write)(u32 reg, u32 v);
         u64 (*icr_read)(void);
         void (*icr_write)(u32 low, u32 high);
         void (*wait_icr_idle)(void);
@@ -426,6 +434,11 @@ static inline void apic_write(u32 reg, u32 val)
         apic->write(reg, val);
 }
 
+static inline void apic_eoi(void)
+{
+        apic->eoi_write(APIC_EOI, APIC_EOI_ACK);
+}
+
 static inline u64 apic_icr_read(void)
 {
         return apic->icr_read();
@@ -450,6 +463,7 @@ static inline u32 safe_apic_wait_icr_idle(void)
 
 static inline u32 apic_read(u32 reg) { return 0; }
 static inline void apic_write(u32 reg, u32 val) { }
+static inline void apic_eoi(void) { }
 static inline u64 apic_icr_read(void) { return 0; }
 static inline void apic_icr_write(u32 low, u32 high) { }
 static inline void apic_wait_icr_idle(void) { }
@@ -463,7 +477,7 @@ static inline void ack_APIC_irq(void)
          * ack_APIC_irq() actually gets compiled as a single instruction
          * ... yummie.
          */
-        apic_write(APIC_EOI, APIC_EOI_ACK);
+        apic_eoi();
 }
 
 static inline unsigned default_get_apic_id(unsigned long x)