On Thu, 7 Sep 2017, Andy Lutomirski wrote: > Jiri reported a resume-from-hibernation failure triggered by PCID. > The root cause appears to be rather odd. The hibernation asm > restores a CR3 value that comes from the image header. If the image > kernel has PCID on, it's entirely reasonable for this CR3 value to > have one of the low 12 bits set. The restore code restores it with > CR4.PCIDE=0, which means that those low 12 bits are accepted by the > CPU but are either ignored or interpreted as a caching mode. This > is odd, but still works. We blow up later when the image kernel > restores CR4, though, since changing CR4.PCIDE with CR3[11:0] != 0 > is illegal. Boom! > > FWIW, it's entirely unclear to me what's supposed to happen if a PAE > kernel restores a non-PAE image or vice versa. Ditto for LA57.
I've just performed 15 hibernation cycles with current Linus' tree (5969d1bb3082) with these two patches applied on top of it, and I haven't encountered any issue (and the warning in switch_mm_irqs_off() didn't trigger either). > Reported-by: Jiri Kosina <[email protected]> > Fixes: 660da7c9228f ("x86/mm: Enable CR4.PCIDE on supported systems") > Signed-off-by: Andy Lutomirski <[email protected]> Tested-by: Jiri Kosina <[email protected]> Thanks! -- Jiri Kosina SUSE Labs
