[Xen-changelog] [xen-unstable] x86/EFI: fix interrupt and fault handling during runtime services calls

[Xen patchbot-unstable <patchbot@xxxxxxx>]

# HG changeset patch
# User Jan Beulich <jbeulich@xxxxxxxxxx>
# Date 1309549303 -3600
# Node ID 7631c461132000979f05759705c055eb3c975c0b
# Parent  335e96664589dd14dfce7ef72e3fee71ad9c39e3
x86/EFI: fix interrupt and fault handling during runtime services calls

The missing piece was the setting up of an accessible GDT prior to
switching page tables (and reverting to the original setting after
having established the normal page tables again afterwards).

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


diff -r 335e96664589 -r 7631c4611320 xen/arch/x86/efi/runtime.c
--- a/xen/arch/x86/efi/runtime.c        Fri Jul 01 20:31:18 2011 +0100
+++ b/xen/arch/x86/efi/runtime.c        Fri Jul 01 20:41:43 2011 +0100
@@ -44,6 +44,17 @@
     /* prevent fixup_page_fault() from doing anything */
     irq_enter();
 
+    if ( !is_hvm_vcpu(current) && !is_idle_vcpu(current) )
+    {
+        struct desc_ptr gdt_desc = {
+            .limit = LAST_RESERVED_GDT_BYTE,
+            .base  = (unsigned long)(per_cpu(gdt_table, smp_processor_id()) -
+                                     FIRST_RESERVED_GDT_ENTRY)
+        };
+
+        asm volatile ( "lgdt %0" : : "m" (gdt_desc) );
+    }
+
     write_cr3(virt_to_maddr(efi_l4_pgtable));
 
     return cr3;
@@ -52,6 +63,15 @@
 void efi_rs_leave(unsigned long cr3)
 {
     write_cr3(cr3);
+    if ( !is_hvm_vcpu(current) && !is_idle_vcpu(current) )
+    {
+        struct desc_ptr gdt_desc = {
+            .limit = LAST_RESERVED_GDT_BYTE,
+            .base  = GDT_VIRT_START(current)
+        };
+
+        asm volatile ( "lgdt %0" : : "m" (gdt_desc) );
+    }
     irq_exit();
     spin_unlock(&efi_rs_lock);
 }

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