Re: [PATCH RFC v4 00/13] virtio-mem: paravirtualized memory

[Alex Shi]

å 2020/6/5 äå5:08, David Hildenbrand åé:
> 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@xxxxxxxxxxxxxxxxx