[PATCH v12 00/25] Linux RISC-V AIA Support

[Björn Töpel]

Björn Töpel <bjorn at kernel.org> writes:

> Anup Patel <apatel at ventanamicro.com> writes:
>
>> On Tue, Jan 30, 2024 at 1:22 PM Björn Töpel <bjorn at kernel.org> wrote:
>>>
>>> Björn Töpel <bjorn at kernel.org> writes:
>>>
>>> > Anup Patel <apatel at ventanamicro.com> writes:
>>> >
>>> >> The RISC-V AIA specification is ratified as-per the RISC-V international
>>> >> process. The latest ratified AIA specifcation can be found at:
>>> >> https://github.com/riscv/riscv-aia/releases/download/1.0/riscv-interrupts-1.0.pdf
>>> >>
>>> >> At a high-level, the AIA specification adds three things:
>>> >> 1) AIA CSRs
>>> >>    - Improved local interrupt support
>>> >> 2) Incoming Message Signaled Interrupt Controller (IMSIC)
>>> >>    - Per-HART MSI controller
>>> >>    - Support MSI virtualization
>>> >>    - Support IPI along with virtualization
>>> >> 3) Advanced Platform-Level Interrupt Controller (APLIC)
>>> >>    - Wired interrupt controller
>>> >>    - In MSI-mode, converts wired interrupt into MSIs (i.e. MSI generator)
>>> >>    - In Direct-mode, injects external interrupts directly into HARTs
>>> >>
>>> >> For an overview of the AIA specification, refer the AIA virtualization
>>> >> talk at KVM Forum 2022:
>>> >> https://static.sched.com/hosted_files/kvmforum2022/a1/AIA_Virtualization_in_KVM_RISCV_final.pdf
>>> >> https://www.youtube.com/watch?v=r071dL8Z0yo
>>> >>
>>> >> To test this series, use QEMU v7.2 (or higher) and OpenSBI v1.2 (or higher).
>>> >>
>>> >> These patches can also be found in the riscv_aia_v12 branch at:
>>> >> https://github.com/avpatel/linux.git
>>> >>
>>> >> Changes since v11:
>>> >>  - Rebased on Linux-6.8-rc1
>>> >>  - Included kernel/irq related patches from "genirq, irqchip: Convert ARM
>>> >>    MSI handling to per device MSI domains" series by Thomas.
>>> >>    (PATCH7, PATCH8, PATCH9, PATCH14, PATCH16, PATCH17, PATCH18, PATCH19,
>>> >>     PATCH20, PATCH21, PATCH22, PATCH23, and PATCH32 of
>>> >>     https://lore.kernel.org/linux-arm-kernel/20221121135653.208611233@linutronix.de/)
>>> >>  - Updated APLIC MSI-mode driver to use the new WIRED_TO_MSI mechanism.
>>> >>  - Updated IMSIC driver to support per-device MSI domains for PCI and
>>> >>    platform devices.
>>> >
>>> > Thanks for working on this, Anup! I'm still reviewing the patches.
>>> >
>>> > I'm hitting a boot hang in text patching, with this series applied on
>>> > 6.8-rc2. IPI issues?
>>>
>>> Not text patching! One cpu spinning in smp_call_function_many_cond() and
>>> the others are in cpu_relax(). Smells like IPI...
>>
>> I tried bootefi from U-Boot multiple times but can't reproduce the
>> issue you are seeing.
>
> Thanks! I can reproduce without EFI, and simpler command-line:
>
> qemu-system-riscv64 \
>   -bios /path/to/fw_dynamic.bin \
>   -kernel /path/to/Image \
>   -append 'earlycon console=tty0 console=ttyS0' \
>   -machine virt,aia=aplic-imsic \
>   -no-reboot -nodefaults -nographic \
>   -smp 4 \
>   -object rng-random,filename=/dev/urandom,id=rng0 \
>   -device virtio-rng-device,rng=rng0 \
>   -m 4G -chardev stdio,id=char0 -serial chardev:char0
>
> I can reproduce with your upstream riscv_aia_v12 plus the config in the
> gist [1], and all latest QEMU/OpenSBI:
>
> QEMU: 11be70677c70 ("Merge tag 'pull-vfio-20240129' of https://github.com/legoater/qemu into staging")
> OpenSBI: bb90a9ebf6d9 ("lib: sbi: Print number of debug triggers found")
> Linux: d9b9d6eb987f ("MAINTAINERS: Add entry for RISC-V AIA drivers")
>
> Removing ",aia=aplic-imsic" from the CLI above completes the boot (i.e.
> panicking about missing root mount ;-))

More context; The hang is during a late initcall, where an ftrace direct
(register_ftrace_direct()) modification is done.

Stop machine is used to call into __ftrace_modify_call(). Then into the
arch specific patch_text_nosync(), where flush_icache_range() hangs in
flush_icache_all(). From "on_each_cpu(ipi_remote_fence_i, NULL, 1);" to
on_each_cpu_cond_mask() "smp_call_function_many_cond(mask, func, info,
scf_flags, cond_func);" which never returns from "csd_lock_wait(csd)"
right before the end of the function.

Any ideas? Disabling CONFIG_HID_BPF, that does the early ftrace code
patching fixes the boot hang, but it does seem related to IPI...