On Mon, Nov 16, 2015 at 08:01:03PM +0100, Ard Biesheuvel wrote: > On 16 November 2015 at 19:55, Russell King - ARM Linux > <linux@xxxxxxxxxxxxxxxx> wrote: > > I'm slightly worried about this. Generally, these functions setup > > global mappings. If you're wanting to have a private set of page > > tables for UEFI, and those private page tables contain global > > mappings which are different from the mappings in the kernel's page > > tables, then you need careful break-TLBflush-make handling when > > switching from the kernel's page tables to the private UEFI ones, > > and vice versa. > > > > Has this aspect been considered? > > Yes. The UEFI mappings are all below 1 GB, and the top kernel end is > reused as we do for ordinary userland page tables. The switch to the > UEFI page tables performs a full TLB flush. What it does not do is > break before make, as far as I can tell, so any pointers regarding how > to implement that would be appreciated (this is implemented in 11/12) What matters is whether they are global mappings or not. If they are, when the TLB can contain conflicting entries. If they are non-global mappings, they will be tagged with the ASID which makes them unique to each mm. The simple solution is to ensure that they're non-global, and then you don't need to even worry about flushing the TLB when switching. -- FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net. -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
