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SubjectRe: [PATCH] adjust/fix LDT handling for Xen
Jan Beulich wrote:
>>>> Ingo Molnar <mingo@elte.hu> 14.01.08 16:48 >>>
>>>>
>> * Jan Beulich <jbeulich@novell.com> wrote:
>>
>>
>>> 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.
>>>
>> coul dyou try this against x86.git as well? We already unified ldt.c as
>> part of the paravirt patches.
>>
>
> Sure, but it may take me a little while.

I've got the unified version here.

Subject: xen: adjust/fix LDT handling for Xen

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>
Cc: Ingo Molnar <mingo@elte.hu>

---
arch/x86/kernel/ldt.c | 7 +++----
arch/x86/xen/enlighten.c | 9 +--------
2 files changed, 4 insertions(+), 12 deletions(-)

===================================================================
--- 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, i
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, i
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 *m
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;
}
}
===================================================================
--- 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);


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