Re: [PATCH] xen: fix allocation and use of large ldts

[Jeremy Fitzhardinge]

Ingo Molnar wrote:
> * Jeremy Fitzhardinge <jeremy@xxxxxxxx> wrote:
>
>   
> > When the ldt gets to more than 1 page in size, the kernel uses vmalloc
> > to allocate it.  This means that:
> > - when making the ldt RO, we must update the pages in both the vmalloc
> >   mapping and the linear mapping to make sure there are no RW aliases.
> > - we need to use arbitrary_virt_to_machine to compute the machine addr
> >   for each update
> >     
>
> applied to tip/x86/xen, thanks Jeremy.
>   

Thanks.  Here's a follow-up tidy patch.

Subject: xen: tidy up ldt fixes

Add a proper comment for set_aliased_prot() and fix an
unsigned long/void * warning.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
---
arch/x86/xen/enlighten.c |    9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

===================================================================
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -395,8 +395,10 @@
}

/*
- * If 'v' is a vmalloc mapping, then find the linear mapping of the
- * page (if any) and also set its protections to match:
+ * Set the page permissions for a particular virtual address.  If the
+ * address is a vmalloc mapping (or other non-linear mapping), then
+ * find the linear mapping of the page and also set its protections to
+ * match.
 */
static void set_aliased_prot(void *v, pgprot_t prot)
{
@@ -545,8 +547,7 @@
static void xen_write_ldt_entry(struct desc_struct *dt, int entrynum,
				const void *ptr)
{
-	unsigned long lp = (unsigned long)&dt[entrynum];
-	xmaddr_t mach_lp = arbitrary_virt_to_machine(lp);
+	xmaddr_t mach_lp = arbitrary_virt_to_machine(&dt[entrynum]);
	u64 entry = *(u64 *)ptr;

	preempt_disable();


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