The purpose of this series is to remove any explicit cache maintenance for coherency during early boot that becomes unnecessary if we simply retain the cacheable 1:1 mapping of all of system RAM provided by EFI, and use it to populate the ID map page tables. After setting up this preliminary ID map, we disable the MMU, drop to EL1, reprogram the MAIR, TCR and SCTLR registers as before, and proceed as usual, avoiding the need for any manipulations of memory while the MMU and caches are off. The only properties of the firmware provided 1:1 map we rely on is that it does not require any explicit cache maintenance for coherency, and that it covers the entire memory footprint of the image, including the BSS and padding at the end - all else is under control of the kernel itself, as before. Changes since v3: - drop EFI_LOADER_CODE memory type patch that has been queued in the mean time - rebased onto [partial] series that moves efi-entry.S into the libstub/ source directory [0] - fixed a correctness issue in patch #2 [0] https://lore.kernel.org/all/20221017171700.3736890-1-ardb@xxxxxxxxxx/ Applying the last patch in the series will require some coordination with the EFI tree, but I can manage that using a secondary 'late' PR during the merge window, if needed. Cc: Will Deacon <will@xxxxxxxxxx> Cc: Catalin Marinas <catalin.marinas@xxxxxxx> Cc: Marc Zyngier <maz@xxxxxxxxxx> Cc: Mark Rutland <mark.rutland@xxxxxxx> Ard Biesheuvel (6): arm64: lds: reduce effective minimum image alignment to 64k arm64: kernel: move identity map out of .text mapping arm64: head: record the MMU state at primary entry arm64: head: avoid cache invalidation when entering with the MMU on arm64: head: clean the ID map page to the PoC arm64: efi/libstub: enter with the MMU on arch/arm64/include/asm/efi.h | 7 -- arch/arm64/kernel/head.S | 70 +++++++++++++++----- arch/arm64/kernel/image-vars.h | 5 +- arch/arm64/kernel/vmlinux.lds.S | 13 +++- arch/arm64/mm/cache.S | 5 +- arch/arm64/mm/proc.S | 2 - drivers/firmware/efi/libstub/arm64-entry.S | 57 ---------------- drivers/firmware/efi/libstub/arm64-stub.c | 19 +++++- include/linux/efi.h | 6 +- 9 files changed, 89 insertions(+), 95 deletions(-) delete mode 100644 drivers/firmware/efi/libstub/arm64-entry.S -- 2.35.1
