On Mon, 22 Feb 2021 16:08:04 +0100 Christian Schoenebeck <qemu_...@crudebyte.com> wrote:
[...] > I did not ever have a kernel crash when I boot a Linux guest with a 9pfs root > fs and 100 MiB msize. Interesting. > Should we ask virtio or 9p Linux client maintainers if > they can add some info what this is about? > Probably worth to try that first, even if I'm not sure anyone has a answer for that since all the people who worked on virtio-9p at the time have somehow deserted the project. > > > As the kernel code sais trans_mod->maxsize, maybe its something in virtio > > > on qemu side that does an automatic step back for some reason. I don't > > > see something in the 9pfs virtio transport driver > > > (hw/9pfs/virtio-9p-device.c on QEMU side) that would do this, so I would > > > also need to dig deeper. > > > > > > Do you have some RAM limitation in your setup somewhere? > > > > > > For comparison, this is how I started the VM: > > > > > > ~/git/qemu/build/qemu-system-x86_64 \ > > > -machine pc,accel=kvm,usb=off,dump-guest-core=off -m 2048 \ > > > -smp 4,sockets=4,cores=1,threads=1 -rtc base=utc \ > > > -boot strict=on -kernel /home/bee/vm/stretch/boot/vmlinuz-4.9.0-13-amd64 \ > > > -initrd /home/bee/vm/stretch/boot/initrd.img-4.9.0-13-amd64 \ > > > -append 'root=svnRoot rw rootfstype=9p > > > rootflags=trans=virtio,version=9p2000.L,msize=104857600,cache=mmap > > > console=ttyS0' \ > > First obvious difference I see between your setup and mine is that > > you're mounting the 9pfs as root from the kernel command line. For > > some reason, maybe this has an impact on the check in p9_client_create() ? > > > > Can you reproduce with a scenario like Vivek's one ? > > Yep, confirmed. If I boot a guest from an image file first and then try to > manually mount a 9pfs share after guest booted, then I get indeed that msize > capping of just 512 kiB as well. That's far too small. :/ > Maybe worth digging : - why no capping happens in your scenario ? - is capping really needed ? Cheers, -- Greg > Best regards, > Christian Schoenebeck > >
