On Mon, Feb 08, 2016 at 10:31:36AM -0500, Boris Ostrovsky wrote:
> This range is reserved for hypervisors but the only hypervisor that uses it
> is Xen PV (lguest doesn't run in 64-bit mode).
Yeah, this is mentioned in arch/x86/include/asm/page_64_types.h:
/*
* Set __PAGE_OFFSET to the most negative possible address +
* PGDIR_SIZE*16 (pgd slot 272). The gap is to allow a space for a
* hypervisor to fit. Choosing 16 slots here is arbitrary, but it's
* what Xen requires.
*/
#define __PAGE_OFFSET _AC(0xffff880000000000, UL)
It is also in Documentation/x86/x86_64/mm.txt:
ffff800000000000 - ffff87ffffffffff (=43 bits) guard hole, reserved for
hypervisor
albeit a bit laconic.
Thanks.
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
