On Tue, Mar 6, 2018 at 3:24 PM, Marc Zyngier <marc.zyngier@xxxxxxx> wrote: > On 05/03/18 14:36, Mark Rutland wrote: >> On Fri, Mar 02, 2018 at 08:44:25PM +0100, Andrey Konovalov wrote: >>> KHWASAN uses the Top Byte Ignore feature of arm64 CPUs to store a pointer >>> tag in the top byte of each pointer. This commit enables the TCR_TBI1 bit, >>> which enables Top Byte Ignore for the kernel, when KHWASAN is used. >>> --- >>> arch/arm64/include/asm/pgtable-hwdef.h | 1 + >>> arch/arm64/mm/proc.S | 8 +++++++- >>> 2 files changed, 8 insertions(+), 1 deletion(-) >> >> Before it's safe to do this, I also think you'll need to fix up at >> least: >> >> * virt_to_phys() >> >> * access_ok() >> >> ... and potentially others which assume that bits [63:56] of kernel >> addresses are 0xff. For example, bits of the fault handling logic might >> need fixups. > > Indeed. I have the ugly feeling that KVM (and anything that leaves in a > separate address space) will not be very happy with that change, as it > derives HYP VAs from the kernel VA, and doesn't expect lingering bits. > Nothing that cannot be addressed, but worth keeping in mind. > Hi Marc! Yes, I would expect there would be issues with KVM. I'll see if I can figure them out, but I think I'll just add a depends on !KVM or something like this, and will have to deal with KVM once the main part is committed. Thanks!
