DMA failures on AMD64 with 4 GB RAM

[Søren Schmidt]

Attila Nagy wrote:
> Hello,
> 
> There is a problem with recent ATA drivers on (at least) AMD64 with 4 GB 
> of RAM, which can be triggered by synchronizing a geom mirror provider 
> to another one (or generally a bigger disk I/O, I guess).
> 
> The machine dies instantly with the following:
> GEOM_MIRROR: Device hars: rebuilding provider ad6.
> ad6: setting up DMA failed
> ad6: setting up DMA failed
> 
> This is true either on RELENG_6 and on HEAD as of today.
> 
> There are two workarounds:
> - use the ata driver from RELENG_6 which is not older than 2005.10.08
> - set hw.physmem smaller than 4G
> 
> Are there any chances to resolve this issue?
> 
> Thank you.
> 
> ps: there was some discussion about this:
> http://marc.theaimsgroup.com/?l=freebsd-amd64&m=113034973432742&w=2
> where Søren said it might be busdma, not the ata driver and Scott 
> promised to look into that.

The resolution was that busdma doesn't work as advertised in the man 
page, and that scottl would look into it.

-Søren
>