Hi Stefano,
On 4/30/19 10:02 PM, Stefano Stabellini wrote:
Reserved memory regions are automatically remapped to dom0. Their device
tree nodes are also added to dom0 device tree. However, the dom0 memory
node is not currently extended to cover the reserved memory regions
ranges as required by the spec. This commit fixes it.
AFAICT, this does not cover the problem mention by Amit in [1].
But I am still not happy with the approach taken for the reserved-memory
regions in this series. As I pointed out before, they are just normal
memory that was reserved for other purpose (CMA, framebuffer...).
Treating them as "device" from Xen POV is a clear abuse of the meaning
and I don't believe it is a viable solution long term.
Indeed, some of the regions may have a property "reusable" allowing the
the OS to use them until they are claimed by the device driver owning
the region. I don't know how Linux (or any other OS) is using it today,
but I don't see what would prevent it to use them as hypercall buffer.
This would obviously not work because they are not actual RAM from Xen POV.
On a similar topic, because they are normal memory, I don't think
XEN_DOMCTL_memory_mapping should be able to map reserved-regions. So the
iomem rangeset should not contain them.
Cheers,
[1] <CABHD4K-z-x=3joJWcOb_x9m7zsjzhskDQweNBr+paLS=pfe...@mail.gmail.com>
--
Julien Grall
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