On Mon, Sep 21, 2026 at 10:50:41PM +0530, Shrikanth Hegde wrote: > Hi Michal, > > On 9/21/26 10:16 PM, Michal Suchánek wrote: > > On Mon, Sep 21, 2026 at 10:06:22AM +0200, Michal Suchánek wrote: > > > On Thu, Sep 03, 2026 at 03:28:26PM +0200, Michal Suchánek wrote: > > > > On Thu, Sep 03, 2026 at 06:06:16PM +0530, Harsh Prateek Bora wrote: > > > > > + Amit, Gautam - since they recently came across a similar regression > > > > > which > > > > > is seen with non KVM workload as well. > > > > > + Venkat - for CI improvement suggestion below. > > > > > > > > > > Hi Michal, > > > > > > > > > > On 03/09/26 5:55 pm, Michal Suchánek wrote: > > > > > > > > > > > > > > > > There is another problem that Linux 7.2.2 often locks up on boot > > > > > > inside > > > > > > the guest, and as a result a different kernel is needed in the > > > > > > guest to > > > > > > reproduce the host crash. This is more recent, linux 6.12 does not > > > > > > have > > > > > > this problem. Will try some different kernel combinations to see if > > > > > > I > > > > > > can narrow this down. For this the repro is merely booting the > > > > > > kernel in > > > > > > the VM, it typically fails early before userspace produces any > > > > > > messages. > > > > > > > > This one regressed between 6.19.12 > > > > https://github.com/openSUSE/kernel-source/blob/9f6830f/config/ppc64le/default > > > > and 7.0.12 > > > > https://github.com/openSUSE/kernel-source/blob/2ebf0bc/config/ppc64le/default > > > > > > Which is when preempt was enabled. > > > > > > Very likely preexisting problem that was exposed by enabling preemption > > > again. > > > > > > @@ -121,9 +122,7 @@ CONFIG_BPF_LSM=y > > > CONFIG_PREEMPT_BUILD=y > > > CONFIG_ARCH_HAS_PREEMPT_LAZY=y > > > -# CONFIG_PREEMPT_NONE is not set > > > -CONFIG_PREEMPT_VOLUNTARY=y > > > -# CONFIG_PREEMPT is not set > > > +CONFIG_PREEMPT=y > > > # CONFIG_PREEMPT_LAZY is not set > > > CONFIG_PREEMPT_COUNT=y > > > CONFIG_PREEMPTION=y > > > > Looking more into this the problem is not reproducible with 6.19 with > > full preempt, and can be reproduced with 7.0 with full preempt where > > preemtion is mandatory. It only so happens that 1.19 was last kernel > > where preemption was not mandatory and where this problem also happened > > to not manifest with the Tumbleweed config. > > > > I am bit confused. Is it different problem than the kprobe/bpf issue > which was observed on host?
Yes, it appears to be different, a crash very early during boot with a different stack trace. > > Is this kvm/guest specific problem you are observing? Is it still seen > even with that kprobe/bpf fix? Yes, even with the fix this can be observed. > > > It is not deterministic enough to bisect. It's probably some kind of > > race condition or code generation problem that can surface and go away > > or become too difficult to reproduce with seemingly unrelated changes. > > > > Can you try latest kernel? How much latest? I tried with 7.2.6 with the kprobe fix as guest, and some earlier 7.2.x as host already, and the problem is reproducible. Thanks Michal > > There was change recently to move to use > generic transfer to guest mode work. i.e VIRT_XFER_TO_GUEST_WORK. > > > Crash happens very early but it's eemu so the memory can be saved > > regardelss. The problem is that the crash tool refuses to load the core > > bacause it detects the core as SMP and vmlinux as non-SMP or the other > > way around. > > > > Thanks > > > > Michal > >
