On Mon, Jan 07, 2019 at 02:03:15PM -0600, Wei Huang wrote: > On 1/7/19 2:25 AM, Kirill A. Shutemov wrote: > > On Fri, Jan 04, 2019 at 05:44:11AM +0000, Wei Huang wrote: > >> In some old AMD KVM implementation, guest's EFER.LME bit is cleared by KVM > >> when the hypervsior detects guest sets CR0.PG to 0. This causes guest OS > >> to reboot when it tries to return from 32-bit trampoline code because CPU > >> is in incorrect state: CR4.PAE=1, CR0.PG=1, CS.L=1, but EFER.LME=0. > >> As a precaution, this patch sets EFER.LME=1 as part of long mode > >> activation procedure. This extra step won't cause any harm when Linux is > >> booting on bare-metal machine. > >> > >> Signed-off-by: Wei Huang <wei@xxxxxxxxxx> > > > > Thanks for tracking this down. > > BTW I think this patch _might_ be related the recent reboot issue > reported in https://lkml.org/lkml/2018/7/1/836 since the symptoms are > exactly the same. The problem in that case turned out to be https://lkml.org/lkml/2018/7/4/723 which was fixed by d503ac531a. --Benjamin Gilbert
