x86: adjust/fix LDT handling for Xen

Based on patch from Jan Beulich <jbeulich@novell.com>.

Don't rely on kmalloc(PAGE_SIZE) returning PAGE_SIZE aligned memory
(Xen requires GDT *and* LDT to be page-aligned). Using the page
allocator interface also removes the (albeit small) slab allocator
overhead. The same change being done for 64-bits for consistency.

Further, the Xen hypercall interface expects the LDT address to be
virtual, not machine.

[ Adjusted to unified ldt.c - Jeremy ]

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Acked-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

2 files changed, 4 insertions, 12 deletions

diff --git a/arch/x86/kernel/ldt.c b/arch/x86/kernel/ldt.c
index b8ef46270e24..8a7660c8394a 100644
--- a/arch/x86/kernel/ldt.c
+++ b/arch/x86/kernel/ldt.c
@@ -12,7 +12,6 @@
 #include <linux/mm.h>
 #include <linux/smp.h>
 #include <linux/vmalloc.h>
-#include <linux/slab.h>
 
 #include <asm/uaccess.h>
 #include <asm/system.h>
@@ -40,7 +39,7 @@ static int alloc_ldt(mm_context_t *pc, int mincount, int reload)
         if (mincount * LDT_ENTRY_SIZE > PAGE_SIZE)
                 newldt = vmalloc(mincount * LDT_ENTRY_SIZE);
         else
-                newldt = kmalloc(mincount * LDT_ENTRY_SIZE, GFP_KERNEL);
+                newldt = (void *)__get_free_page(GFP_KERNEL);
 
         if (!newldt)
                 return -ENOMEM;
@@ -78,7 +77,7 @@ static int alloc_ldt(mm_context_t *pc, int mincount, int reload)
                 if (oldsize * LDT_ENTRY_SIZE > PAGE_SIZE)
                         vfree(oldldt);
                 else
-                        kfree(oldldt);
+                        put_page(virt_to_page(oldldt));
         }
         return 0;
 }
@@ -129,7 +128,7 @@ void destroy_context(struct mm_struct *mm)
                 if (mm->context.size * LDT_ENTRY_SIZE > PAGE_SIZE)
                         vfree(mm->context.ldt);
                 else
-                        kfree(mm->context.ldt);
+                        put_page(virt_to_page(mm->context.ldt));
                 mm->context.size = 0;
         }
 }
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 72dd14d0685c..845b4fd94463 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -275,19 +275,12 @@ static unsigned long xen_store_tr(void)
 
 static void xen_set_ldt(const void *addr, unsigned entries)
 {
-        unsigned long linear_addr = (unsigned long)addr;
         struct mmuext_op *op;
         struct multicall_space mcs = xen_mc_entry(sizeof(*op));
 
         op = mcs.args;
         op->cmd = MMUEXT_SET_LDT;
-        if (linear_addr) {
-                /* ldt my be vmalloced, use arbitrary_virt_to_machine */
-                xmaddr_t maddr;
-                maddr = arbitrary_virt_to_machine((unsigned long)addr);
-                linear_addr = (unsigned long)maddr.maddr;
-        }
-        op->arg1.linear_addr = linear_addr;
+        op->arg1.linear_addr = (unsigned long)addr;
         op->arg2.nr_ents = entries;
 
         MULTI_mmuext_op(mcs.mc, op, 1, NULL, DOMID_SELF);