On Sun, 2 Sep 2018, Linus Torvalds wrote: > Which basically doesn't happen on x86 in reality. BIOSes just don't put > MMIO right after the last page of RAM. I think this is why it only > triggered on Xen, due to some crazy "Xen reacts badly" case where we do > the speculation into a balloon address. > > So _practically_ this is just a Xen bug, nothing more.
Yeah, and Xen guys are already working on fixing that AFAIK. > But since in _theory_ you could have MMIO abut regular RAM directly, > it's worth maybe making sure it's purely theory. Well, we've been hit by similar/related issue in practice, on x86 machines where GART aperture is being mapped over physical RAM. For the curious -- see commit 2a3e83c6f ("x86/gart: Exclude GART aperture from vmcore"). Thanks, -- Jiri Kosina SUSE Labs