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. Thanks, M. -- Jazz is not dead. It just smells funny... -- 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>
