Re: Libvirt on little.BIG ARM systems unable to start guest if no cpuset is provided

On Tue, Dec 14, 2021 at 09:34:18AM +0000, Marc Zyngier wrote: > On Tue, 14 Dec 2021 00:41:01 +0000, > Qu Wenruo <quwenruo.btrfs(a)gmx.com&gt; wrote: >> >> >> >> On 2021/12/14 00:49, Marc Zyngier wrote: >>> On Mon, 13 Dec 2021 16:06:14 +0000, >>> Peter Maydell <peter.maydell(a)linaro.org&gt; wrote: >>>> >>>> KVM on big.little setups is a kernel-level question really; I've >>>> cc'd the kvmarm list. >>> >>> Thanks Peter for throwing us under the big-little bus! ;-) >>> >>>> >>>> On Mon, 13 Dec 2021 at 15:02, Qu Wenruo <quwenruo.btrfs(a)gmx.com&gt; wrote: >>>>> >>>>> >>>>> >>>>> On 2021/12/13 21:17, Michal Prívozník wrote: >>>>>> On 12/11/21 02:58, Qu Wenruo wrote: >>>>>>> Hi, >>>>>>> >>>>>>> Recently I got my libvirt setup on both RK3399 (RockPro64) and RPI CM4, >>>>>>> with upstream kernels. >>>>>>> >>>>>>> For RPI CM4 its mostly smooth sail, but on RK3399 due to its little.BIG >>>>>>> setup (core 0-3 are 4x A55 cores, and core 4-5 are 2x A72 cores), it >>>>>>> brings quite some troubles for VMs. >>>>>>> >>>>>>> In short, without proper cpuset to bind the VM to either all A72 cores >>>>>>> or all A55 cores, the VM will mostly fail to boot. >>> >>> s/A55/A53/. There were thankfully no A72+A55 ever produced (just the >>> though of it makes me sick). >>> >>>>>>> >>>>>>> Currently the working xml is: >>>>>>> >>>>>>> <vcpu placement='static' cpuset='4-5'>2</vcpu> >>>>>>> <cpu mode='host-passthrough' check='none'/> >>>>>>> >>>>>>> But even with vcpupin, pinning each vcpu to each physical core, VM will >>>>>>> mostly fail to start up due to vcpu initialization failed with -EINVAL. >>> >>> Disclaimer: I know nothing about libvirt (and no, I don't want to >>> know! ;-). >>> >>> However, for things to be reliable, you need to taskset the whole QEMU >>> process to the CPU type you intend to use. >> >> Yep, that's what I'm doing. > > Are you sure? The xml directive above seem to only apply to the vcpus, > and no other QEMU thread. For historical reasons this XML element is a bit misleadingly named. With the config <vcpu placement='static' cpuset='4-5'>2</vcpu> the 'cpuset' applies to the QEMU process as a whole - its vCPUs, I/O threads and any other emulator threads. There is a separate config for setting per-VCPU binding which was illustrated elsewhere in this thread.

Regards, Daniel