Re: [Xen-devel] [PATCH v4 5/8] xen/arm: assign devices to boot domains

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Tue, 24 Sep 2019, Julien Grall wrote:
> Hi Stefano,
> 
> On 9/24/19 5:52 PM, Stefano Stabellini wrote:
> > On Wed, 11 Sep 2019, Julien Grall wrote:
> > > It also raises the question what should we do if the size passed in not
> > > page-aligned? Shall we just blindly round up/down? Should we warn?
> > > 
> > > This was not important for dom0, but is potentially critical for domU as
> > > you
> > > may happen to inadvertently to export more than you hope to a guest.
> > 
> > A warning or even a panic would be OK because it is a static
> > misconfiguration.
> 
> Yes and no, there are platforms where devices are sharing the same pages (see
> the UART on Sunxi SoC for instance). So this is a valid configuration, but we
> don't support it.

Hopefully the user should know that the minimum granularity is 4K.


> The problem does not arise for domU created by the toolstack because we
> request a frame. Note that I would not want to use a frame for Dom0less
> assignment as I think this is buggy.
> 
> Anyway, I would rather not add a panic in this code and let the upper layer
> deciding what to do.

OK. I added a warning.

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