Linux Virtualization - Jun 2020 - [PATCH RFC v4 00/13] virtio-mem: paravirtualized memory

? 2020/1/9 ??9:48, David Hildenbrand ??:
> Ping,
> 
> I'd love to get some feedback on
> 
> a) The remaining MM bits from MM folks (especially, patch #6 and #8).
> b) The general virtio infrastructure (esp. uapi in patch #2) from virtio
> folks.
> 
> I'm planning to send a proper v1 (!RFC) once I have all necessary MM
> acks. In the meanwhile, I will do more testing and minor reworks (e.g.,
> fix !CONFIG_NUMA compilation).

Hi David,

Thanks for your work!

I am trying your https://github.com/davidhildenbrand/linux.git virtio-mem-v5
which works fine for me, but just a 'DMA error' happens when a vm start
with
less than 2GB memory, Do I missed sth?

Thanks
Alex


(qemu) qom-set vm0 requested-size 1g
(qemu) [   26.560026] virtio_mem virtio0: plugged size: 0x0
[   26.560648] virtio_mem virtio0: requested size: 0x40000000
[   26.561730] systemd-journald[167]: no db file to read
/run/udev/data/+virtio:virtio0: No such file or directory
[   26.563138] systemd-journald[167]: no db file to read
/run/udev/data/+virtio:virtio0: No such file or directory
[   26.569122] Built 1 zonelists, mobility grouping on.  Total pages: 513141
[   26.570039] Policy zone: Normal

(qemu) [   32.175838] e1000 0000:00:03.0: swiotlb buffer is full (sz: 81 bytes),
total 0 (slots), used 0 (slots)
[   32.176922] e1000 0000:00:03.0: TX DMA map failed
[   32.177488] e1000 0000:00:03.0: swiotlb buffer is full (sz: 81 bytes), total
0 (slots), used 0 (slots)
[   32.178535] e1000 0000:00:03.0: TX DMA map failed

my qemu command is like this:
qemu-system-x86_64  --enable-kvm \
	-m 2G,maxmem=16G -kernel /root/linux-next/$1/arch/x86/boot/bzImage \
	-smp 4 \
	-append "earlyprintk=ttyS0 root=/dev/sda1 console=ttyS0 debug psi=1
nokaslr ignore_loglevel" \
	-hda /root/CentOS-7-x86_64-Azure-1703.qcow2 \
	-net user,hostfwd=tcp::2222-:22 -net nic -s \
  -object memory-backend-ram,id=mem0,size=3G \
  -device virtio-mem-pci,id=vm0,memdev=mem0,node=0,requested-size=0M \
	--nographic

On 05.06.20 10:55, Alex Shi wrote:
> 
> 
> ? 2020/1/9 ??9:48, David Hildenbrand ??:
>> Ping,
>>
>> I'd love to get some feedback on
>>
>> a) The remaining MM bits from MM folks (especially, patch #6 and #8).
>> b) The general virtio infrastructure (esp. uapi in patch #2) from
virtio
>> folks.
>>
>> I'm planning to send a proper v1 (!RFC) once I have all necessary
MM
>> acks. In the meanwhile, I will do more testing and minor reworks (e.g.,
>> fix !CONFIG_NUMA compilation).
> 
> 
> Hi David,
> 
> Thanks for your work!
> 
> I am trying your https://github.com/davidhildenbrand/linux.git
virtio-mem-v5
> which works fine for me, but just a 'DMA error' happens when a vm
start with
> less than 2GB memory, Do I missed sth?
Please use the virtio-mem-v4 branch for now, v5 is still under
construction (and might be scrapped completely if v4 goes upstream as is).

Looks like a DMA issue. Your're hotplugging 1GB, which should not really
eat too much memory. There was a similar issue reported by Hui in [1],
which boiled down to wrong usage of the swiotlb parameter.

In such cases you should always try to reproduce with hotplug of a
sam-sized DIMM. E.g., hotplugging a 1GB DIMM should result in the same
issue.

What does your .config specify for CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE?

I'll try to reproduce with v4 briefly.

[1]
https://lkml.kernel.org/r/9708F43A-9BD2-4377-8EE8-7FB1D95C6F69 at
linux.alibaba.com
> 
> Thanks
> Alex
> 
> 
> (qemu) qom-set vm0 requested-size 1g
> (qemu) [   26.560026] virtio_mem virtio0: plugged size: 0x0
> [   26.560648] virtio_mem virtio0: requested size: 0x40000000
> [   26.561730] systemd-journald[167]: no db file to read
/run/udev/data/+virtio:virtio0: No such file or directory
> [   26.563138] systemd-journald[167]: no db file to read
/run/udev/data/+virtio:virtio0: No such file or directory
> [   26.569122] Built 1 zonelists, mobility grouping on.  Total pages:
513141
> [   26.570039] Policy zone: Normal
> 
> (qemu) [   32.175838] e1000 0000:00:03.0: swiotlb buffer is full (sz: 81
bytes), total 0 (slots), used 0 (slots)
> [   32.176922] e1000 0000:00:03.0: TX DMA map failed
> [   32.177488] e1000 0000:00:03.0: swiotlb buffer is full (sz: 81 bytes),
total 0 (slots), used 0 (slots)
> [   32.178535] e1000 0000:00:03.0: TX DMA map failed
> 
> my qemu command is like this:
> qemu-system-x86_64  --enable-kvm \
> 	-m 2G,maxmem=16G -kernel /root/linux-next/$1/arch/x86/boot/bzImage \
> 	-smp 4 \
> 	-append "earlyprintk=ttyS0 root=/dev/sda1 console=ttyS0 debug psi=1
nokaslr ignore_loglevel" \
> 	-hda /root/CentOS-7-x86_64-Azure-1703.qcow2 \
> 	-net user,hostfwd=tcp::2222-:22 -net nic -s \
>   -object memory-backend-ram,id=mem0,size=3G \
>   -device virtio-mem-pci,id=vm0,memdev=mem0,node=0,requested-size=0M \
> 	--nographic
> 
> 

-- 
Thanks,

David / dhildenb

On 05.06.20 11:08, David Hildenbrand wrote:
> On 05.06.20 10:55, Alex Shi wrote:
>>
>>
>> ? 2020/1/9 ??9:48, David Hildenbrand ??:
>>> Ping,
>>>
>>> I'd love to get some feedback on
>>>
>>> a) The remaining MM bits from MM folks (especially, patch #6 and
#8).
>>> b) The general virtio infrastructure (esp. uapi in patch #2) from
virtio
>>> folks.
>>>
>>> I'm planning to send a proper v1 (!RFC) once I have all
necessary MM
>>> acks. In the meanwhile, I will do more testing and minor reworks
(e.g.,
>>> fix !CONFIG_NUMA compilation).
>>
>>
>> Hi David,
>>
>> Thanks for your work!
>>
>> I am trying your https://github.com/davidhildenbrand/linux.git
virtio-mem-v5
>> which works fine for me, but just a 'DMA error' happens when a
vm start with
>> less than 2GB memory, Do I missed sth?
> 
> Please use the virtio-mem-v4 branch for now, v5 is still under
> construction (and might be scrapped completely if v4 goes upstream as is).
> 
> Looks like a DMA issue. Your're hotplugging 1GB, which should not
really
> eat too much memory. There was a similar issue reported by Hui in [1],
> which boiled down to wrong usage of the swiotlb parameter.
> 
> In such cases you should always try to reproduce with hotplug of a
> sam-sized DIMM. E.g., hotplugging a 1GB DIMM should result in the same
> issue.
> 
> What does your .config specify for CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE?
> 
> I'll try to reproduce with v4 briefly.
I guess I know what's happening here. In case we only have DMA memory
when booting, we don't reserve swiotlb buffers. Once we hotplug memory
and online ZONE_NORMAL, we don't have any swiotlb DMA bounce buffers to
map such PFNs (total 0 (slots), used 0 (slots)).

Can you try with "swiotlb=force" on the kernel cmdline?

-- 
Thanks,

David / dhildenb

? 2020/6/5 ??5:08, David Hildenbrand ??:
> Please use the virtio-mem-v4 branch for now, v5 is still under
> construction (and might be scrapped completely if v4 goes upstream as is).
> 
> Looks like a DMA issue. Your're hotplugging 1GB, which should not
really
> eat too much memory. There was a similar issue reported by Hui in [1],
> which boiled down to wrong usage of the swiotlb parameter.
I have no swiotbl=noforce set, and sometime no swiotlb error reported, like
(qemu) [   41.591308] e1000 0000:00:03.0: dma_direct_map_page: overflow
0x000000011fd470da+54 of device mask ffffffff
[   41.592431] e1000 0000:00:03.0: TX DMA map failed
[   41.593031] e1000 0000:00:03.0: dma_direct_map_page: overflow
0x000000011fd474da+54 of device mask ffffff
...
[   63.049464] ata_piix 0000:00:01.1: dma_direct_map_sg: overflow
0x0000000107db2000+4096 of device mask ffffffff
[   63.068297] ata1.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x0
[   63.069057] ata1.00: failed command: READ DMA
[   63.069580] ata1.00: cmd c8/00:20:40:bd:d2/00:00:00:00:00/e0 tag 0 dma 16384
in
[   63.069580]          res 50/00:00:3f:30:80/00:00:00:00:00/a0 Emask 0x40
(internal error) 
> 
> In such cases you should always try to reproduce with hotplug of a
> sam-sized DIMM. E.g., hotplugging a 1GB DIMM should result in the same
> issue.
> 
> What does your .config specify for CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE?
Yes, it's set. 

I had tried the v2/v4 version, which has the same issue.
Is this related with virtio-mem start address too low?

Thanks a lot!
> 
> I'll try to reproduce with v4 briefly.
> 
> [1]
> https://lkml.kernel.org/r/9708F43A-9BD2-4377-8EE8-7FB1D95C6F69 at
linux.alibaba.com