On 14.05.20 13:10, David Hildenbrand wrote:

On 14.05.20 12:12, David Hildenbrand wrote:

quoted

On 14.05.20 12:02, teawater wrote:

quoted

quoted

2020年5月14日 16:48，David Hildenbrand [off-list ref] 写道：

On 14.05.20 08:44, teawater wrote:

quoted

Hi David,

I got a kernel warning with v2 and v3.

Hi Hui,

thanks for playing with the latest versions. Surprisingly, I can
reproduce even by hotplugging a DIMM instead as well - that's good, so
it's not related to virtio-mem, lol. Seems to be some QEMU setup issue
with older machine types.

Can you switch to a newer qemu machine version, especially
pc-i440fx-5.0? Both, hotplugging DIMMs and virtio-mem works for me with
that QEMU machine just fine.

I still could reproduce this issue with pc-i440fx-5.0 or pc.  Did I miss anything?

Below I don't even see virtio_mem. I had to repair the image (filesystem
fsck) because it was broken, can you try that as well?

Also, it would be great if you could test with v4.

Correction, something seems to be broken either in QEMU or the kernel. Once I
define a DIMM so it's added and online during boot, I get these issues:

(I have virtio-mem v4 installed in the guest)

#! /bin/bash
sudo x86_64-softmmu/qemu-system-x86_64 \
    -machine pc-i440fx-5.0,accel=kvm,usb=off \
    -cpu host \
    -no-reboot \
    -nographic \
    -device ide-hd,drive=hd \
    -drive if=none,id=hd,file=/home/dhildenb/git/Fedora-Cloud-Base-31-1.9.x86_64.qcow2,format=qcow2 \
    -m 1g,slots=10,maxmem=2G \
    -smp 1 \
    -object memory-backend-ram,id=mem0,size=256m \
    -device pc-dimm,id=dimm0,memdev=mem0 \
    -s \
    -monitor unix:/var/tmp/monitor,server,nowait


Without the DIMM it seems to work just fine.

And another correction. 

Using QEMU v5.0.0, Linux 5.7-rc5, untouched
Fedora-Cloud-Base-32-1.6.x86_64.qcow2, I get even without any memory hotplug:

#! /bin/bash
sudo x86_64-softmmu/qemu-system-x86_64 \
    -machine pc-i440fx-5.0,accel=kvm,usb=off \
    -cpu host \
    -no-reboot \
    -nographic \
    -device ide-hd,drive=hd \
    -drive if=none,id=hd,file=/home/dhildenb/git/Fedora-Cloud-Base-32-1.6.x86_64.qcow2,format=qcow2 \
    -m 5g,slots=10,maxmem=6G \
    -smp 1 \
    -s \
    -kernel /home/dhildenb/git/linux/arch/x86/boot/bzImage \
    -append "console=ttyS0 rd.shell nokaslr swiotlb=noforce" \
    -monitor unix:/var/tmp/monitor,server,nowait


Observe how big the initial RAM even is!


So this is no DIMM/hotplug/virtio_mem issue. With memory hotplug, it seems to get
more likely to trigger if "swiotlb=noforce" is not specified.

"swiotlb=noforce" seems to trigger some pre-existing issue here. Without
"swiotlb=noforce", I was only able to observe this via pc-i440fx-2.1,

-- 
Thanks,

David / dhildenb