On 15/09/2020 17:00, Heinrich Schuchardt wrote:
On 15.09.20 16:50, Grant Likely wrote:
On 15/09/2020 15:36, Heinrich Schuchardt wrote:
On 15.09.20 16:16, Ard Biesheuvel wrote:
[...]>>>> EfiRuntimeServicesData is not covered by the linear map, but
will map
it in the EFI page tables for access by the firmware itself at
runtime, so it is not an option here.
The device-tree spec specifically says /mmemreserve/ serve to "define an
entry for the devicetree blob’s memory reservation table."
I think this is just poorly worded. It would be better written as:
"Memory reservations create entries in the devicetree blob’s
memory reservation table."
Shouldn't the description of /memreserve/ refer to chapter 5.3 Memory
Reservation Block? E.g.
"Memory reservations blocks (see chapter 5.3) are represented by lines
of the form
/memreserve/ <address> <length>;
where <address> and <length> are 64-bit C-style integers, e.g.
/memreserve/ 0x10000000 0x0004000;"
I like that language & layout. I've pulled it into the draft patch. Thanks!
Some requirements in chapter 5.3.1 sound similar to the description of
the no-map sub-nodes of /reserved-memory, e.g. speculative access is
prohibited:
"Any memory that is declared in a memory node and is accessed by the
boot program or caused to be accessed by the boot program after client
entry must be reserved. Examples of this type of access include (e.g.,
speculative memory reads through a non-guarded virtual page)."
So in line with our discussion concerning no-map EfiReservedMemoryType
seems the most appropriate.
UEFI runtime drivers will be relocated by SetVirtualMemoryMap(). So the
requirement in the above citation does not make much sense for memory
that is EfiRuntimeServicesCode or EfiRuntimeServicesData. So those
should not be modeled as /memreserve/. Just another issue with the DT spec.
Okay. I'm convinced. I'll specify EfiReservedMemoryType for memreserve.
g.
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