This is v4 of the series to update the UEFI memory map handling for the arm64 architecture so that virtual mappings of UEFI Runtime Services are stable across kexec. To de-risk the adoption of the subset of patches that are essential to get kexec working on UEFI systems, in this v4 I dropped all the patches related to the iomem resource table, /dev/mem permissions and memory attributes etc. These topics will be revisited asap in a separate series. The primary changes with respect to v3 in the patches that were kept are: - instead of reording the memory map so that part of it can double as input argument to SetVirtualAddressMap(), increase the allocation size for the memory map so that we can use some of it as scratch space and use that to prepare the input to SVAM() instead. - added some acks - rebased onto v3.19-rc1 NOTE: these changes trigger an issue on AMD Seattle that we (Mark Rutland and I) consider a firmware bug. It appears that, during the call to SVAM() (which is called with a 1:1 mapping as per the UEFI spec) the virtual mapping being installed is dereferenced prematurely. This went unnoticed in the original situation, as the virtual mappings were just kernel mappings that are always accessible. However, in the new situation, those mappings are only active during Runtime Service invocations, and performing any kind of access through them at any other time triggers a fault. ============== v1 blurb ================== The main premise of these patches is that, in order to support kexec, we need to add code to the kernel that is able to deal with the state of the firmware after SetVirtualAddressMap() [SVAM] has been called. However, if we are going to deal with that anyway, why not make that the default state, and have only a single code path for both cases. This means SVAM() needs to move to the stub, and hence the code that invents the virtual layout needs to move with it. The result is that the kernel proper is entered with the virt_addr members of all EFI_MEMORY_RUNTIME regions assigned, and the mapping installed into the firmware. The kernel proper needs to set up the page tables, and switch to them while performing the runtime services calls. Note that there is also an efi_to_phys() to translate the values of the fw_vendor and tables fields of the EFI system table. Again, this is something we need to do anyway under kexec, or we end up handing over state between one kernel and the next, which implies different code paths between non-kexec and kexec. The layout is chosen such that it used the userland half of the virtual address space (TTBR0), which means no additional alignment or reservation is required to ensure that it will always be available. One thing that may stand out is the reordering of the memory map. The reason for doing this is that we can use the same memory map as input to SVAM(). The alternative is allocating memory for it using boot services, but that clutters up the existing logic a bit between getting the memory map, populating the fdt, and loop again if it didn't fit. Ard Biesheuvel (8): arm64/mm: add explicit struct_mm argument to __create_mapping() arm64/mm: add create_pgd_mapping() to create private page tables efi: split off remapping code from efi_config_init() efi: efistub: allow allocation alignment larger than EFI_PAGE_SIZE arm64/efi: set EFI_ALLOC_ALIGN to 64 KB arm64/efi: move SetVirtualAddressMap() to UEFI stub arm64/efi: remove free_boot_services() and friends arm64/efi: remove idmap manipulations from UEFI code arch/arm64/include/asm/efi.h | 24 +- arch/arm64/include/asm/mmu.h | 5 +- arch/arm64/include/asm/pgtable.h | 5 + arch/arm64/kernel/efi.c | 360 ++++++++----------------- arch/arm64/kernel/setup.c | 2 +- arch/arm64/mm/mmu.c | 60 ++--- drivers/firmware/efi/efi.c | 49 ++-- drivers/firmware/efi/libstub/efi-stub-helper.c | 25 +- drivers/firmware/efi/libstub/fdt.c | 137 +++++++++- include/linux/efi.h | 2 + 10 files changed, 348 insertions(+), 321 deletions(-) -- 1.8.3.2 -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
