Re: [Xen-devel] Assigning contiguous memory to a driver domain

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

>>> On 15.09.10 at 14:06, Rafal Wojtczuk <rafal@xxxxxxxxxxxxxxxxxxxxxx> wrote:
> It is not too convincing, either. Firstly, assuming there is no dom0mem
> parameter to Xen, dom0 gets all memory initially, so when dom0 boots the
> first time, Xen free memory = 0 ? And drivers load fine.

Xen reserves 1/16th of the memory (up to 128Mb) in this case for this
very purpose. Otherwise, Dom0 would neither be able to set up its
swiotlb nor would any coherent/consistent allocations work.

> Secondly, by default on Fedora, the pm-utils scripts tell NetworkManager to
> turn off networking just before entering S3 sleep, and NetworkManager downs 
> all
> interfaces. It brings them up on resume. And apparently there are some
> drivers, like tg3, that needs to alloc when bringing up the device. Still,
> suspend/resume works when all devices are assigned to dom0.

Because on suspend the driver frees the memory which on resume
it will allocate back?

> Is it possible that swiotlb layer works differently in dom0 case ? Swiotlb
> is switched on by default in dom0 case, is it correct ?

Of course.

Jan


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