linux-kernel - Re: [v4 PATCH 0/3] Add UEFI support for RISC-V

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Date:   Tue, 21 Apr 2020 13:59:50 -0700 (PDT)
From:   Palmer Dabbelt <palmer@...belt.com>
To:     ardb@...nel.org
CC:     Atish Patra <Atish.Patra@....com>, linux-kernel@...r.kernel.org,
        linux-efi@...r.kernel.org, linux-riscv@...ts.infradead.org,
        masahiroy@...nel.org, xypron.glpk@....de
Subject:     Re: [v4 PATCH 0/3] Add UEFI support for RISC-V

On Tue, 21 Apr 2020 00:24:04 PDT (-0700), ardb@...nel.org wrote:
> On Tue, 21 Apr 2020 at 05:34, Atish Patra <atish.patra@....com> wrote:
>>
>> This series adds UEFI support for RISC-V. Currently, only boot time
>> services have been added. Runtime services will be added in a separate
>> series. This series depends on some core EFI patches
>> present in current in efi-next and following other patches.
>>
>> U-Boot: Adds the boot hartid under chosen node.
>> https://lists.denx.de/pipermail/u-boot/2020-April/405726.html
>>
>> Linux kernel: 5.7-rc1
>>
>> OpenSBI: master
>>
>> Patch 1 just moves arm-stub code to a generic code so that it can be used
>> across different architecture.
>>
>> Patch 3 adds fixmap bindings so that CONFIG_EFI can be compiled and we do not
>> have create separate config to enable boot time services.
>> As runtime services are not enabled at this time, full generic early ioremap
>> support is also not added in this series.
>>
>> Patch 4 and 5 adds the PE/COFF header and EFI stub code support for RISC-V
>> respectively.
>>
>> The patches can also be found in following git repo.
>>
>> https://github.com/atishp04/linux/tree/wip_uefi_riscv_v4
>>
>> The patches have been verified on Qemu using bootefi command in U-Boot.
>>
>> Changes from v3->v4:
>> 1. Rebased on top of efi-next.
>> 2. Dropped patch 1 & 2 from this series as it is already queued in efi-next.
>> Changes from v2->v3:
>> 3. Improved handle_kernel_image() for RISC-V.
>>
>
> Thanks Atish. This looks nice and simple now.
>
> I will need an ack from the RISC-V maintainers on these, and it is up
> to them to consider whether the changes to core kconfigs and makefiles
> are likely to cause trouble or not. If so, I am happy to work out a
> way to merge this via a shared stable branch.

Sorry it took me a while to get around to these, but they're essentially good
with me.  There's some comments about needing ISA_C/c.li, but that's pretty
trivial.  In terms of mechanics: I don't really ever understand how to do these
multi-tree merges.  In an ideal world I'd like to have the arch/riscv/ stuff
stay in riscv/for-next, both because I don't want to deal with merge conflicts
and because that's where the RISC-V autobuilders look.

The best I can come up with is to split #3 up such that drivers/firmware/efi/
is its own patch and then send that up along with the PE header definitions
into an RC.  It'd be unused code at that point, but at least it'd break the
dependency between the trees and it'll be getting tested in riscv/for-next so
it won't rot.  We can ARMSTUB->GENERIC_STUB by just having the RISC-V support
select woth ARMSTUB and GENERIC_STUB, with a cleanup going in after everything
is merged.

That said, I'm happy if there's a better way to do this...

>> Changes from v1->v2:
>> 1. Rebased on 5.7-rc1.
>> 2. Fixed minor typos and removed redundant macros/comments.
>>
>> Changes from previous version:
>> 1. Renamed to the generic efi stub macro.
>> 2. Address all redundant comments.
>> 3. Supported EFI kernel image with normal booti command.
>> 4. Removed runtime service related macro defines.
>>
>> Atish Patra (3):
>> RISC-V: Define fixmap bindings for generic early ioremap support
>> RISC-V: Add PE/COFF header for EFI stub
>> RISC-V: Add EFI stub support.
>>
>> arch/riscv/Kconfig                        |  21 +++++
>> arch/riscv/Makefile                       |   1 +
>> arch/riscv/configs/defconfig              |   1 +
>> arch/riscv/include/asm/Kbuild             |   1 +
>> arch/riscv/include/asm/efi.h              |  44 +++++++++
>> arch/riscv/include/asm/fixmap.h           |  18 ++++
>> arch/riscv/include/asm/io.h               |   1 +
>> arch/riscv/include/asm/sections.h         |  13 +++
>> arch/riscv/kernel/Makefile                |   4 +
>> arch/riscv/kernel/efi-header.S            |  99 ++++++++++++++++++++
>> arch/riscv/kernel/head.S                  |  16 ++++
>> arch/riscv/kernel/image-vars.h            |  53 +++++++++++
>> arch/riscv/kernel/vmlinux.lds.S           |  20 +++-
>> drivers/firmware/efi/Kconfig              |   2 +-
>> drivers/firmware/efi/libstub/Makefile     |  10 ++
>> drivers/firmware/efi/libstub/riscv-stub.c | 106 ++++++++++++++++++++++
>> 16 files changed, 407 insertions(+), 3 deletions(-)
>> create mode 100644 arch/riscv/include/asm/efi.h
>> create mode 100644 arch/riscv/include/asm/sections.h
>> create mode 100644 arch/riscv/kernel/efi-header.S
>> create mode 100644 arch/riscv/kernel/image-vars.h
>> create mode 100644 drivers/firmware/efi/libstub/riscv-stub.c
>>
>> --
>> 2.24.0
>>