On Sep 2, 2015 5:46 AM, "Jan Beulich" <[email protected]> wrote: > > While commit 37868fe113 ("x86/ldt: Make modify_ldt synchronous") added > a nice comment explaining that Xen needs page-aligned whole page chunks > for guest descriptor tables, it then nevertheless used kzalloc() on the > small size path. As I'm unaware of guarantees for kmalloc(PAGE_SIZE, ) > to return page-aligned memory blocks, I believe this needs to be > switched back to __get_free_page(). > > Signed-off-by: Jan Beulich <[email protected]> > Cc: Andy Lutomirski <[email protected]> > Cc: Boris Ostrovsky <[email protected]> > Cc: David Vrabel <[email protected]> > Cc: Konrad Rzeszutek Wilk <[email protected]> > --- > v2: Also adjust the freeing side. > --- > arch/x86/kernel/ldt.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > --- 4.2/arch/x86/kernel/ldt.c > +++ 4.2-x86-LDT-alloc/arch/x86/kernel/ldt.c > @@ -58,7 +58,7 @@ static struct ldt_struct *alloc_ldt_stru > if (alloc_size > PAGE_SIZE) > new_ldt->entries = vzalloc(alloc_size); > else > - new_ldt->entries = kzalloc(PAGE_SIZE, GFP_KERNEL); > + new_ldt->entries = (void > *)__get_free_page(GFP_KERNEL|__GFP_ZERO); > > if (!new_ldt->entries) { > kfree(new_ldt); > @@ -95,7 +95,7 @@ static void free_ldt_struct(struct ldt_s > if (ldt->size * LDT_ENTRY_SIZE > PAGE_SIZE) > vfree(ldt->entries); > else > - kfree(ldt->entries); > + put_page(virt_to_page(ldt->entries));
FWIW, I'm not convinced this is or was correct. Using free_page looks a bit safer, and free_page does more than just put_page. Does anyone here know the right way to do this? --Andy > kfree(ldt); > } > > > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
