Hello! > -----Original Message----- > From: kvm-owner@xxxxxxxxxxxxxxx [mailto:kvm-owner@xxxxxxxxxxxxxxx] On Behalf Of Pavel Fedin > Sent: Tuesday, December 01, 2015 1:03 PM > To: 'Marc Zyngier'; kvmarm@xxxxxxxxxxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx > Cc: 'Ard Biesheuvel'; christoffer.dall@xxxxxxxxxx > Subject: RE: BUG ALERT: ARM32 KVM does not work in 4.4-rc3 > > Hello! > > > > My project involves ARM64, but from time to time i also test ARM32 > > > KVM. I have discovered that it stopped working in 4.4-rc3. The same > > > virtual machine works perfectly under current kvmarm/next, but gets > > > stuck at random point under 4.4-rc3 from linux-stable. I'm not sure > > > that i have time to investigate this quickly, but i'll post some new > > > information as soon as i get it > > [skip] > > > So until you bisect it to an exact commit and configuration, I declare > > the alert over. ;-) > > The commit in question is e6fab54423450d699a09ec2b899473a541f61971 ("ARM/arm64: KVM: test > properly for a PTE's uncachedness"). > Reverting it fixes the problem. > Study in qemu shows that the CPU gets stuck at PC = 0x0C with LR = 0x10. So i quickly decided > that it might have to do with > caching, and my first hit was correct. The guest crashes in this state very early, sometimes > it even cannot fully print > "Uncompressing kernel". > The machine which reproduces it is custom Samsung's out-of-tree board. I'll investigate it > further in order to determine how > exactly the commit could harm. I know that it passed reviews and testing, and i was involved > too. Perhaps it's board's code fault, > however. > > Cc'ed to others involved. The problem seems to be triggered by ARCH_SPARSEMEM_ENABLE. My top-secret machine uses it, while more widespread things like vexpress and Exynos don't. Kind regards, Pavel Fedin Expert Engineer Samsung Electronics Research center Russia -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
