On 16 November 2015 at 20:48, Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> wrote: > On Mon, Nov 16, 2015 at 08:04:00PM +0100, Ard Biesheuvel wrote: >> OK. So you mean set TTBR to the zero page, perform the TLB flush and >> only then switch to the new page tables? > > Not quite. > > If you have global mappings below TASK_SIZE, you would need this > sequence when switching either to or from the UEFI page tables: > > - switch to another set of page tables which only map kernel space > with nothing at all in userspace. > - flush the TLB. > - switch to your target page tables. > Doh. I am so used to always having two TTBR's available, but indeed, we shouldn't pull the rug from under our feet. > As I say in response to one of your other patches, it's probably > much easier to avoid any global mappings below TASK_SIZE. Let me look into that. Thanks, Ard. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>