x86: x2apic pre-enabled but intr-remapping is not enabled

Make it aligned with Linux kernel.

Signed-off-by: Yinghai Lu <yinghai@xxxxxxxxxx>

Removed unnecessary bits from the original patch, and removed
intremap_enabled() with its only caller gone.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>

--- 2010-11-09.orig/xen/arch/x86/apic.c
+++ 2010-11-09/xen/arch/x86/apic.c
@@ -972,15 +972,6 @@ void x2apic_setup(void)
     rdmsrl(MSR_IA32_APICBASE, msr_content);
     if ( msr_content & MSR_IA32_APICBASE_EXTD )
     {
-        /*
-         * Interrupt remapping should be also enabled by BIOS when
-         * x2APIC is already enabled by BIOS, otherwise it's a BIOS
-         * bug
-         */
-        if ( !intremap_enabled() )
-            panic("Interrupt remapping is not enabled by BIOS while "
-                  "x2APIC is already enabled by BIOS!\n");
-
         printk("x2APIC mode is already enabled by BIOS.\n");
         x2apic_enabled = 1;
     }
@@ -1023,6 +1014,10 @@ void x2apic_setup(void)
 
     if ( iommu_enable_IR() )
     {
+        if ( x2apic_enabled )
+            panic("Interrupt remapping could not be enabled while "
+                  "x2APIC is already enabled by BIOS!\n");
+
         printk("Would not enable x2APIC due to interrupt remapping "
                "cannot be enabled.\n");
         goto restore_out;
--- 2010-11-09.orig/xen/drivers/passthrough/vtd/intremap.c
+++ 2010-11-09/xen/drivers/passthrough/vtd/intremap.c
@@ -894,23 +894,3 @@ void iommu_disable_IR(void)
     for_each_drhd_unit ( drhd )
         disable_qinval(drhd->iommu);
 }
-
-/*
- * Check if interrupt remapping is enabled or not
- * return 1: enabled
- * return 0: not enabled
- */
-int intremap_enabled(void)
-{
-    struct acpi_drhd_unit *drhd;
-    u32 sts;
-
-    for_each_drhd_unit ( drhd )
-    {
-        sts = dmar_readl(drhd->iommu->reg, DMAR_GSTS_REG);
-        if ( !(sts & DMA_GSTS_IRES) )
-            return 0;
-    }
-
-    return 1;
-}
--- 2010-11-09.orig/xen/include/xen/iommu.h
+++ 2010-11-09/xen/include/xen/iommu.h
@@ -62,7 +62,6 @@ int iommu_setup(void);
 int iommu_supports_eim(void);
 int iommu_enable_IR(void);
 void iommu_disable_IR(void);
-int intremap_enabled(void);
 
 int iommu_add_device(struct pci_dev *pdev);
 int iommu_remove_device(struct pci_dev *pdev);