xen/apic: implement io apic read with hypercall

Implements xen_io_apic_read with hypercall, so it returns proper
IO-APIC information instead of fabricated one.

Fallback to return an emulated IO_APIC values if hypercall fails.

[v2: fallback to return an emulated IO_APIC values if hypercall fails]
Signed-off-by: Lin Ming <mlin@ss.pku.edu.cn>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/arch/x86/xen/apic.c b/arch/x86/xen/apic.c
index 73ade38caa32..1913bf2d2a9c 100644
--- a/arch/x86/xen/apic.c
+++ b/arch/x86/xen/apic.c
@@ -1,8 +1,21 @@
 #include <linux/init.h>
 #include <asm/x86_init.h>
+#include <asm/apic.h>
+#include <xen/interface/physdev.h>
+#include <asm/xen/hypercall.h>
 
 unsigned int xen_io_apic_read(unsigned apic, unsigned reg)
 {
+        struct physdev_apic apic_op;
+        int ret;
+
+        apic_op.apic_physbase = mpc_ioapic_addr(apic);
+        apic_op.reg = reg;
+        ret = HYPERVISOR_physdev_op(PHYSDEVOP_apic_read, &apic_op);
+        if (!ret)
+                return apic_op.value;
+
+        /* fallback to return an emulated IO_APIC values */
         if (reg == 0x1)
                 return 0x00170020;
         else if (reg == 0x0)