[coreboot-gerrit] [L] Change in coreboot[main]: acpi: Add PPTT support

[Nico Huber (Code Review)]

Attention is currently required from: Angel Pons, Arthur Heymans, Cliff Huang, David Milosevic, Lance Zhao, Martin L Roth, Maximilian Brune, Patrick Rudolph, Tim Wawrzynczak.

Nico Huber has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/78071?usp=email )

Change subject: acpi: Add PPTT support
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Patch Set 22:

(2 comments)

File src/acpi/acpi_pptt.c:

https://review.coreboot.org/c/coreboot/+/78071/comment/979d23c9_454403f3 :
PS17, Line 131: cache_reference_t cache_refs[CONFIG_ACPI_PPTT_MAX_CACHES];
> > Looks like https://uefi. […]

Well, QEMU-SBSA is a rather simple example, with a homogenuous hierarchy
and caches known at compile time. I just wonder how it will look like for
a more complex setup when one has to allocate `struct pptt_cache` nodes
at runtime. Then it would be harder to reuse the nodes and their pointers.
But I guess we can handle that if/when the time comes.

File src/include/acpi/acpi.h:

https://review.coreboot.org/c/coreboot/+/78071/comment/1e014ee7_d84a9707 :
PS21, Line 1448: 	u32 size_valid          : 1;
               : 		u32 n_sets_valid        : 1;
               : 		u32 associativity_valid : 1;
               : 		u32 alloc_type_valid    : 1;
               : 		u32 cache_type_valid    : 1;
               : 		u32 write_policy_valid  : 1;
               : 		u32 line_size_valid     : 1;
               : 		u32 cache_id_valid      : 1;
               : 		u32 reserved            : 24;
> Are bitfields portable? Or can they break depending on endianness?

Bitfields or not, unless the table is defined to be in host
endianness, all serialization of multi-byte words would break
with a different endianness. Not sure about ACPI. I think we
decided some time ago not to care about big-endian anymore
(I disagree, but much of our code is broken in that regard
anyway. If we'd ever start from scratch, I wouldn't use structs
for serialization).