Re: [PATCH] firewire: Enable remote DMA above 4 GB
From: Stefan Richter
Date: Sat Jan 18 2014 - 11:05:54 EST
On Jan 18 Stefan Richter wrote:
> This makes all of a machine's memory accessible to remote debugging via
> FireWire, using the physical response unit (i.e. RDMA) of OHCI-1394 link
> layer controllers.
> This requires actual support by the controller. The only ones currently
> known to support it are Agere/LSI FW643. Most if not all other OHCI-1394
> controllers do not implement the optional Physical Upper Bound register.
> With them, RDMA will continue to be limited to the lowermost 4 GB.
this patch does not switch remote DMA on.
It only increases the range of remote access to all memory (instead of just
4 GB) _when_ remote DMA was switched on by other means. The latter is
achieved by setting CONFIG_FIREWIRE_OHCI_REMOTE_DMA, or by a module
parameter introduced by commit 8bc588e0e585 of linux1394.git, or if the
physical DMA filter is opened through firewire-sbp2.
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