Re: [Xen-devel] DL385 G2 - PCI-DMA: Random memory would be DMAed

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 18/10/07 20:05, "Zachary Richmond" <zak@xxxxxxxxxxx> wrote:

> Regarding the full error message, all I am getting is:
> 
> kernel panic not syncing: PCI-DMA: Random memory would be DMAed
> 
> since the machine is rebooting after that.  There maybe somewhere else to get
> more detail, but beyond dmesg or messages I am not sure where else to look.

You should also get a line immediately before that saying:
"PCI-DMA: Out of SW-IOMMU space for xxx bytes at device xxx"

This message makes it clear that your swiotlb is not big enough. The default
size is 2MB if your machine has less than 2GB RAM. Otherwise the default is
64MB. You can increase the swiotlb size by, for example, adding
'swiotlb=128' as a boot parameter to your dom0 kernel (the example here
would set the swiotlb size to be 128MB).

Setting the parameter too small will make your system crash (as you have
seen). Setting it bigger than necessary will waste memory. The optimum
setting will depend on your system.

 -- Keir



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