1 files changed, 33 insertions, 0 deletions

diff --git a/drivers/kvm/x86.c b/drivers/kvm/x86.c
index b84cb6707f78..5a959220410a 100644
--- a/drivers/kvm/x86.c
+++ b/drivers/kvm/x86.c
@@ -16,16 +16,49 @@
 
 #include "kvm.h"
 #include "x86.h"
+#include "segment_descriptor.h"
 #include "irq.h"
 
 #include <linux/kvm.h>
 #include <linux/fs.h>
 #include <linux/vmalloc.h>
+#include <linux/module.h>
 
 #include <asm/uaccess.h>
 
 #define MAX_IO_MSRS 256
 
+unsigned long segment_base(u16 selector)
+{
+        struct descriptor_table gdt;
+        struct segment_descriptor *d;
+        unsigned long table_base;
+        unsigned long v;
+
+        if (selector == 0)
+                return 0;
+
+        asm("sgdt %0" : "=m"(gdt));
+        table_base = gdt.base;
+
+        if (selector & 4) {           /* from ldt */
+                u16 ldt_selector;
+
+                asm("sldt %0" : "=g"(ldt_selector));
+                table_base = segment_base(ldt_selector);
+        }
+        d = (struct segment_descriptor *)(table_base + (selector & ~7));
+        v = d->base_low | ((unsigned long)d->base_mid << 16) |
+                ((unsigned long)d->base_high << 24);
+#ifdef CONFIG_X86_64
+        if (d->system == 0 && (d->type == 2 || d->type == 9 || d->type == 11))
+                v |= ((unsigned long) \
+                      ((struct segment_descriptor_64 *)d)->base_higher) << 32;
+#endif
+        return v;
+}
+EXPORT_SYMBOL_GPL(segment_base);
+
 /*
  * List of msr numbers which we expose to userspace through KVM_GET_MSRS
  * and KVM_SET_MSRS, and KVM_GET_MSR_INDEX_LIST.