iommu/vt-d: Prepare for killing function irq_remapping_supported()

Prepare for killing function irq_remapping_supported() by moving code
from intel_irq_remapping_supported() into intel_prepare_irq_remapping().

Combined with patch from Joerg at https://lkml.org/lkml/2014/12/15/487,
so assume an signed-off from Joerg.

Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Tested-by: Joerg Roedel <joro@8bytes.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: iommu@lists.linux-foundation.org
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Link: http://lkml.kernel.org/r/1420615903-28253-9-git-send-email-jiang.liu@linux.intel.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 25 insertions, 33 deletions

diff --git a/drivers/iommu/intel_irq_remapping.c b/drivers/iommu/intel_irq_remapping.c
index 1e7e09327753..8ccc7aa7e43a 100644
--- a/drivers/iommu/intel_irq_remapping.c
+++ b/drivers/iommu/intel_irq_remapping.c
@@ -568,30 +568,6 @@ static int __init dmar_x2apic_optout(void)
 
 static int __init intel_irq_remapping_supported(void)
 {
-        struct dmar_drhd_unit *drhd;
-        struct intel_iommu *iommu;
-
-        if (disable_irq_remap)
-                return 0;
-        if (irq_remap_broken) {
-                printk(KERN_WARNING
-                        "This system BIOS has enabled interrupt remapping\n"
-                        "on a chipset that contains an erratum making that\n"
-                        "feature unstable.  To maintain system stability\n"
-                        "interrupt remapping is being disabled.  Please\n"
-                        "contact your BIOS vendor for an update\n");
-                add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_STILL_OK);
-                disable_irq_remap = 1;
-                return 0;
-        }
-
-        if (!dmar_ir_support())
-                return 0;
-
-        for_each_iommu(iommu, drhd)
-                if (!ecap_ir_support(iommu->ecap))
-                        return 0;
-
         return 1;
 }
 
@@ -616,26 +592,42 @@ static int __init intel_prepare_irq_remapping(void)
         struct dmar_drhd_unit *drhd;
         struct intel_iommu *iommu;
 
+        /* First check whether IRQ remapping should be enabled */
+        if (disable_irq_remap)
+                return -ENODEV;
+
+        if (irq_remap_broken) {
+                printk(KERN_WARNING
+                        "This system BIOS has enabled interrupt remapping\n"
+                        "on a chipset that contains an erratum making that\n"
+                        "feature unstable.  To maintain system stability\n"
+                        "interrupt remapping is being disabled.  Please\n"
+                        "contact your BIOS vendor for an update\n");
+                add_taint(TAINT_FIRMWARE_WORKAROUND, LOCKDEP_STILL_OK);
+                disable_irq_remap = 1;
+                return -ENODEV;
+        }
+
         if (dmar_table_init() < 0)
-                return -1;
+                return -ENODEV;
+
+        if (!dmar_ir_support())
+                return -ENODEV;
 
         if (parse_ioapics_under_ir() != 1) {
                 printk(KERN_INFO "Not enabling interrupt remapping\n");
                 goto error;
         }
 
-        for_each_iommu(iommu, drhd) {
-                if (!ecap_ir_support(iommu->ecap))
-                        continue;
-
-                /* Do the allocations early */
-                if (intel_setup_irq_remapping(iommu))
+        for_each_iommu(iommu, drhd)
+                if (!ecap_ir_support(iommu->ecap) ||
+                    intel_setup_irq_remapping(iommu))
                         goto error;
-        }
         return 0;
+
 error:
         intel_cleanup_irq_remapping();
-        return -1;
+        return -ENODEV;
 }
 
 static int __init intel_enable_irq_remapping(void)