Hi Luca,
On 09/04/2024 12:45, Luca Fancellu wrote:
Currently Xen is not exporting the static shared memory regions
to the device tree as /memory node, this commit is fixing this
issue.
The static shared memory banks can be part of the memory range
available for the domain, so if they are overlapping with the
normal memory banks, they need to be merged together in order
to produce a /memory node with non overlapping ranges in 'reg'.
Before reviewing the code in more details, I would like to understand a
bit more the use case and whether it should be valid.
From my understanding, the case you are trying to prevent is the
following setup:
1. The Guest Physical region 0x0000 to 0x8000 is used for RAM
2. The Guest Physical region 0x0000 to 0x4000 is used for static memory
The underlying Host Physical regions may be different. Xen doesn't
guarantee in which order the regions will be mapped, So whether the
overlapped region will point to the memory or the shared region is
unknown (we don't guarantee the order of the mapping). So nothing good
will happen to the guest.
Did I understand correctly? If so, shouldn't this be a configuration we
should forbid?
Cheers,
--
Julien Grall
