On Fri, 10 Feb 2023 09:30:18 +0000 Yangming via <qemu-devel@nongnu.org> wrote:
> Hello all: > > I found VM crashed while hot-plugging memory. > > Base infomation: > qemu version: qemu-master > requirements: hugepages, virtio-gpu > > It happens by the following steps: > 1. Booting a VM with hugepages and a virtio-gpu device. > 2. Connecting VNC of the VM. > 3. After the VM booted, hot-plugging 512G memory. > 4. Then you can find that the image in vnc is blocked and the worse thing is > that the VM crashed. > > Actually the vcpu is blocked because of dead lock. > > Analysis: > As when hot-pluging the BQL is held, at the meanwhile, virtio-gpu is trying > to hold the BQL for writing date. Then a vcpu is blocked waiting for > hugepages hot-plugging, specifically, waiting for touching pages. If the > blocked vcpu stops for several seconds, the soft lockup will happen, if it > stops for a long time, e.g. 30s, the VM will crash. > > I am wandering if there are some ideas to avoid VM soft lockup and even VM > crash ? Maybe David can suggest something (CCed) > > Thank you! > kind regards!
