>>> On 02.09.15 at 16:08, <[email protected]> wrote: > 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.
Actually I agree. put_page() is meant to be paired with get_page(); __get_free_pages() is just misleading (i.e. doesn't imply a get_page()) and instead is to be paired with free_pages(). Will do a v3 then. Jan -- 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/
