On 28/02/2019 11:13, Marc Zyngier wrote: > On 28/02/2019 08:49, Marc Zyngier wrote: >> On Thu, 28 Feb 2019 08:16:05 +0000, >> Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: >> >> Hi both, >> >>> >>> On Wed, Feb 27, 2019 at 04:36:39PM -0800, Daniel Verkamp wrote: >>>> Hello, >>>> >>>> In my testing of crosvm[1] with Linux 4.4.175, I am observing failures >>>> on a 'kevin' Chromebook (RK3399) device - the guest kernel does not >>>> even get to the point of printing its first messages, and the host >>>> seems to be spinning at 100% CPU in KVM_RUN. >>>> >>>> I narrowed this down to the 4.4 stable backport of "arm64: KVM: Skip >>>> MMIO insn after emulation" - with this patch reverted, I can boot the >>>> guest kernel as normal again. >>>> >>>> Unfortunately, I am unable to easily test with a newer upstream kernel >>>> (this board is using the Chrome OS kernel with many additional patches >>>> applied on top of 4.4), so I'm not sure if this issue was introduced >>>> in the mainline commit or only in the stable branch. Is it possible >>>> that this patch has other dependencies that were missed in the >>>> backport? It looks like it was part of a larger series, but only this >>>> patch got pulled for 4.4 stable. >> >> Thanks for reporting this. I'll have a look ASAP. >> >>> It looks like this got pulled in by Sasha's bot which is why it was >>> applied. >>> >>> I have no objection to reverting this if it is causing problems, unless >>> someone here really thinks it needs to remain in the tree? >> >> Can we hold on a tiny bit so that I can verify we haven't regressed >> crosvm all the way into mainline? >> >> Daniel, is there any chance you could test with kvmtool as well on >> your setup? You can easily compile it as a static binary and run it >> from ChromeOS with: >> >> lkvm-static run -c 1 -p "earlycon=uart,mmio,0x3f8" -l Image >> >> which should start a UP guest and drop you to a shell. In the >> meantime, I'm starting to build crosvm on my kevin running mainline. > > OK, that wasn't a fun experience. Some build instructions for the mere > mortals (aka non-ChromeOS people) would be nice (and a mention that > crosvm cannot yet deal with GICv3-only systems...) > > Anyway, I've got enough of it working that I can boot a trivial Debian > guest on kevin running 5.0-rc7, so I'm pretty confident that mainline is > OK. I'll move back to 4.4, and try to understand what happens there. I got 4.4.175 running on an AMD Seattle, and this patch broke more than just crosvm. It actually breaks the whole KVM in-kernel device emulation which can't make forward progress (it is forever stuck on the same instruction, writing to the emulated GIC). Both QEMU and kvmtool are also affected. Irk. :-( It turns out 4.4.175 is missing two patches on which $SUBJECT relies: 83091db981e1 KVM: arm/arm64: Fix MMIO emulation data handling 1d6a821277aa arm/arm64: KVM: Feed initialized memory to MMIO accesses which are implicit dependencies for it. With these two patches cherry-picked, I get both kvmtool and crosvm working. Greg: I'll send these two patches backported to 4.4-stable ASAP, so that we don't have to revert anything. Thanks, M. -- Jazz is not dead. It just smells funny...
