x86/ioapic: Add io_apic_ops driver layer to allow interception

Xen dom0 needs to paravirtualize IO operations to the IO APIC,
so add a io_apic_ops for it to intercept.  Do this as ops
structure because there's at least some chance that another
paravirtualized environment may want to intercept these.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: jwboyer@redhat.com
Cc: yinghai@kernel.org
Link: http://lkml.kernel.org/r/1332385090-18056-2-git-send-email-konrad.wilk@oracle.com
[ Made all the affected code easier on the eyes ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 9 insertions, 0 deletions

diff --git a/arch/x86/include/asm/io_apic.h b/arch/x86/include/asm/io_apic.h
index 690d1cc9a877..2c4943de5150 100644
--- a/arch/x86/include/asm/io_apic.h
+++ b/arch/x86/include/asm/io_apic.h
@@ -21,6 +21,15 @@
 #define IO_APIC_REDIR_LEVEL_TRIGGER     (1 << 15)
 #define IO_APIC_REDIR_MASKED            (1 << 16)
 
+struct io_apic_ops {
+        void            (*init)  (void);
+        unsigned int    (*read)  (unsigned int apic, unsigned int reg);
+        void            (*write) (unsigned int apic, unsigned int reg, unsigned int value);
+        void            (*modify)(unsigned int apic, unsigned int reg, unsigned int value);
+};
+
+void __init set_io_apic_ops(const struct io_apic_ops *);
+
 /*
  * The structure of the IO-APIC:
  */