[S] Change in coreboot[main]: device/Kconfig: Add an option to allocate above 4G by default
Attention is currently required from: Arthur Heymans, Chen, Gang C, Jincheng Li, Nico Huber, Paul Menzel.
Shuo Liu has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/78331?usp=email )
Change subject: device/Kconfig: Add an option to allocate above 4G by default ......................................................................
Patch Set 16: Code-Review+1
(3 comments)
Commit Message:
https://review.coreboot.org/c/coreboot/+/78331/comment/243d9813_a75ad20c : PS13, Line 8:
Sometimes, a PCIe host bridge will provide MMIO32 (below 4G) and MMIO64 (above 4G) windows, the opti […]
Done
File src/device/Kconfig:
https://review.coreboot.org/c/coreboot/+/78331/comment/9473d5c7_f58787ad : PS16, Line 1012: config RESOURCE_IGNORE_FLAG_IORESOURCE_ABOVE_4G
I think this deserves a more positive naming. e.g. `ALWAYS_ALLOW_ABOVE_4G_ALLOCATION`.
Acknowledged
https://review.coreboot.org/c/coreboot/+/78331/comment/6ca02944_946920db : PS16, Line 1019: 32bit mode
Technically the incompatible mode is "flat protected mode", or we could […]
Since resource allocation will be programmed into PCI BARs, which provides 64bit BAR register if needed, hence a 32bit bootloader can actually allocate 64bit resources, as long as coreboot will load a driver for this device.
To allocate 64bit resource in a 32bit bootloader but not using it is actually a requirement in various cases. E.g, some device will have >4G BAR preference, but if allocated in <4G space, OS will not modify it any more.
Hence, we even think we could just simply the help message as,
help Don't limit mem resources to 4G, but to their actual limit. (This can break ... -> to be removed)
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Shuo Liu (Code Review)