Rick's recent patch series, which adds support for U-Boot SPL to the Andes platform, brought several problems of the current U-Boot SPL boot flow on RISC-V to light. Discussion on the relevant parts starts at [1].
The problem showed itself in the form of code corruption. At start, OpenSBI relocates itself to its link address. This allows it to be loaded independently of the link address. In the case that the link address ranges of U-Boot SPL and OpenSBI overlap, code corruption occurs if the relocation starts while some harts are still running U-Boot SPL. This series prevents this problem by specifying the hart that performs the relocation and then making sure that it is the last hart to enter OpenSBI, allowing relocation to be completed safely. A recent version of OpenSBI is required for the changes to work.
This patch series resolves the problems associated with the use case of overlapping link address ranges. However, it is still recommended to select non-overlapping ranges for U-Boot SPL and OpenSBI.
[1]: https://lists.denx.de/pipermail/u-boot/2019-November/389385.html
Lukas Auer (4): spl: opensbi: specify main hart as preferred boot hart riscv: add functions for reading the IPI status riscv: add option to wait for ack from secondary harts in smp functions spl: opensbi: wait for ack from secondary harts before entering OpenSBI
arch/riscv/cpu/start.S | 2 ++ arch/riscv/include/asm/smp.h | 3 ++- arch/riscv/lib/andes_plic.c | 9 ++++++++ arch/riscv/lib/bootm.c | 2 +- arch/riscv/lib/sbi_ipi.c | 11 +++++++++ arch/riscv/lib/sifive_clint.c | 9 ++++++++ arch/riscv/lib/smp.c | 43 +++++++++++++++++++++++++++-------- arch/riscv/lib/spl.c | 2 +- common/spl/spl_opensbi.c | 13 ++++++++++- include/opensbi.h | 18 ++++++++++++++- 10 files changed, 98 insertions(+), 14 deletions(-)