On 09/10/2014 10:31 PM, Andrey Ryabinin wrote: > On 09/11/2014 08:01 AM, H. Peter Anvin wrote: >> On 09/10/2014 07:31 AM, Andrey Ryabinin wrote: >>> This patch add arch specific code for kernel address sanitizer. >>> >>> 16TB of virtual addressed used for shadow memory. >>> It's located in range [0xffff800000000000 - 0xffff900000000000] >>> Therefore PAGE_OFFSET has to be changed from 0xffff880000000000 >>> to 0xffff900000000000. >> >> NAK on this. >> >> 0xffff880000000000 is the lowest usable address because we have agreed >> to leave 0xffff800000000000-0xffff880000000000 for the hypervisor or >> other non-OS uses. >> >> Bumping PAGE_OFFSET seems needlessly messy, why not just designate a >> zone higher up in memory? >> > > I already answered to Dave why I choose to place shadow bellow PAGE_OFFSET (answer copied bellow). > In short - yes, shadow could be higher. But for some sort of kernel bugs we could have confusing oopses in kasan kernel. > Confusing how? I presume you are talking about something trying to touch a non-canonical address, which is usually a very blatant type of bug. -hpa -- 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>