Messages in this thread | | | Date | Mon, 3 Sep 2018 08:05:12 +0200 (CEST) | From | Jiri Kosina <> | Subject | Re: Access to non-RAM pages |
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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
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