x86/ioapic: Fix IOAPIC failing to request resource

handle_ioapic_add() uses request_resource() to request ACPI "_CRS"
resources. This can fail with the following error message:

  [  247.325693] ACPI: \_SB_.IIO1.AID1: failed to insert resource

This happens when there are multiple IOAPICs and DSDT groups their
"_CRS" resources as the children of a parent resource, as seen from
/proc/iomem:

  fec00000-fecfffff : PNP0003:00
    fec00000-fec003ff : IOAPIC 0
    fec01000-fec013ff : IOAPIC 1
    fec40000-fec403ff : IOAPIC 2

In this case request_resource() fails because there's a conflicting
resource which is the parent (fec0000-fecfffff). Fix it by using
insert_resource() which can request resources by taking the conflicting
resource as the parent.

Signed-off-by: Rui Wang <rui.y.wang@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: bhelgaas@google.com
Cc: helgaas@kernel.org
Cc: linux-acpi@vger.kernel.org
Cc: linux-pci@vger.kernel.org
Cc: rjw@rjwysocki.net
Cc: tony.luck@intel.com
Link: http://lkml.kernel.org/r/1471420837-31003-6-git-send-email-rui.y.wang@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

drivers/acpi/ioapic.c

@@ -146,10 +146,12 @@ static acpi_status handle_ioapic_add(acpi_handle handle, u32 lvl,
 
 	crs_res = &ioapic->res;
 	acpi_walk_resources(handle, METHOD_NAME__CRS, setup_res, crs_res);
+	crs_res->name = type;
+	crs_res->flags |= IORESOURCE_BUSY;
 	if (crs_res->flags == 0) {
 		acpi_handle_warn(handle, "failed to get resource\n");
 		goto exit_release;
-	} else if (request_resource(&iomem_resource, crs_res)) {
+	} else if (insert_resource(&iomem_resource, crs_res)) {
 		acpi_handle_warn(handle, "failed to insert resource\n");
 		goto exit_release;
 	}