Re: [PATCH 00/10] RISC-V: Refactor instructions

[Jessica Clarke]

On 17 Aug 2023, at 01:31, Charlie Jenkins <charlie@xxxxxxxxxxxx> wrote:
> 
> On Fri, Aug 04, 2023 at 10:24:33AM -0700, Charlie Jenkins wrote:
>> On Fri, Aug 04, 2023 at 12:28:28PM +0300, Andrew Jones wrote:
>>> On Thu, Aug 03, 2023 at 07:10:25PM -0700, Charlie Jenkins wrote:
>>>> There are numerous systems in the kernel that rely on directly
>>>> modifying, creating, and reading instructions. Many of these systems
>>>> have rewritten code to do this. This patch will delegate all instruction
>>>> handling into insn.h and reg.h. All of the compressed instructions, RVI,
>>>> Zicsr, M, A instructions are included, as well as a subset of the F,D,Q
>>>> extensions.
>>>> 
>>>> ---
>>>> This is modifying code that https://lore.kernel.org/lkml/20230731183925.152145-1-namcaov@xxxxxxxxx/
>>>> is also touching.
>>>> 
>>>> ---
>>>> Testing:
>>>> 
>>>> There are a lot of subsystems touched and I have not tested every
>>>> individual instruction. I did a lot of copy-pasting from the RISC-V spec
>>>> so opcodes and such should be correct
>>> 
>>> How about we create macros which generate each of the functions an
>>> instruction needs, e.g. riscv_insn_is_*(), etc. based on the output of
>>> [1]. I know basically nothing about that project, but it looks like it
>>> creates most the defines this series is creating from what we [hope] to
>>> be an authoritative source. I also assume that if we don't like the
>>> current output format, then we could probably post patches to the project
>>> to get the format we want. For example, we could maybe propose an "lc"
>>> format for "Linux C".
>> That's a great idea, I didn't realize that existed!
> I have discovered that the riscv-opcodes repository is not in a state
> that makes it helpful. If it were workable, it would make it easy to
> include a "Linux C" format. I have had a pull request open on the repo
> for two weeks now and the person who maintains the repo has not
> interacted.

Huh? Andrew has replied to you twice on your PR, and was the last one to
comment. That’s hardly “has not interacted”.

> At minimum, in order for it to be useful it would need an ability to
> describe the bit order of immediates in an instruction and include script
> arguments to select which instructions should be included. There is a
> "C" format, but it is actually just a Spike format.

So extend it? Or do something with QEMU’s equivalent that expresses it.

Jess

> Nonetheless, it
> seems like it is prohibitive to use it.
>>> 
>>> I'd also recommend only importing the generated defines and generating
>>> the functions that will actually have immediate consumers or are part of
>>> a set of defines that have immediate consumers. Each consumer of new
>>> instructions will be responsible for generating and importing the defines
>>> and adding the respective macro invocations to generate the functions.
>>> This series can also take that approach, i.e. convert one set of
>>> instructions at a time, each in a separate patch.
>> Since I was hand-writing everything and copying it wasn't too much
>> effort to just copy all of the instructions from a group. However, from
>> a testing standpoint it makes sense to exclude instructions not yet in
>> use.
>>> 
>>> [1] https://github.com/riscv/riscv-opcodes
>>> 
>>> Thanks,
>>> drew
>>> 
>>> 
>>>> , but the construction of every
>>>> instruction is not fully tested.
>>>> 
>>>> vector: Compiled and booted
>>>> 
>>>> jump_label: Ensured static keys function as expected.
>>>> 
>>>> kgdb: Attempted to run the provided tests but they failed even without
>>>> my changes
>>>> 
>>>> module: Loaded and unloaded modules
>>>> 
>>>> patch.c: Ensured kernel booted
>>>> 
>>>> kprobes: Used a kprobing module to probe jalr, auipc, and branch
>>>> instructions
>>>> 
>>>> nommu misaligned addresses: Kernel boots
>>>> 
>>>> kvm: Ran KVM selftests
>>>> 
>>>> bpf: Kernel boots. Most of the instructions are exclusively used by BPF
>>>> but I am unsure of the best way of testing BPF.
>>>> 
>>>> Signed-off-by: Charlie Jenkins <charlie@xxxxxxxxxxxx>
>>>> 
>>>> ---
>>>> Charlie Jenkins (10):
>>>>      RISC-V: Expand instruction definitions
>>>>      RISC-V: vector: Refactor instructions
>>>>      RISC-V: Refactor jump label instructions
>>>>      RISC-V: KGDB: Refactor instructions
>>>>      RISC-V: module: Refactor instructions
>>>>      RISC-V: Refactor patch instructions
>>>>      RISC-V: nommu: Refactor instructions
>>>>      RISC-V: kvm: Refactor instructions
>>>>      RISC-V: bpf: Refactor instructions
>>>>      RISC-V: Refactor bug and traps instructions
>>>> 
>>>> arch/riscv/include/asm/bug.h             |   18 +-
>>>> arch/riscv/include/asm/insn.h            | 2744 +++++++++++++++++++++++++++---
>>>> arch/riscv/include/asm/reg.h             |   88 +
>>>> arch/riscv/kernel/jump_label.c           |   13 +-
>>>> arch/riscv/kernel/kgdb.c                 |   13 +-
>>>> arch/riscv/kernel/module.c               |   80 +-
>>>> arch/riscv/kernel/patch.c                |    3 +-
>>>> arch/riscv/kernel/probes/kprobes.c       |   13 +-
>>>> arch/riscv/kernel/probes/simulate-insn.c |  100 +-
>>>> arch/riscv/kernel/probes/uprobes.c       |    5 +-
>>>> arch/riscv/kernel/traps.c                |    9 +-
>>>> arch/riscv/kernel/traps_misaligned.c     |  218 +--
>>>> arch/riscv/kernel/vector.c               |    5 +-
>>>> arch/riscv/kvm/vcpu_insn.c               |  281 +--
>>>> arch/riscv/net/bpf_jit.h                 |  707 +-------
>>>> 15 files changed, 2825 insertions(+), 1472 deletions(-)
>>>> ---
>>>> base-commit: 5d0c230f1de8c7515b6567d9afba1f196fb4e2f4
>>>> change-id: 20230801-master-refactor-instructions-v4-433aa040da03
>>>> -- 
>>>> - Charlie
>>>> 
>>>> 
>>>> -- 
>>>> kvm-riscv mailing list
>>>> kvm-riscv@xxxxxxxxxxxxxxxxxxx
>>>> http://lists.infradead.org/mailman/listinfo/kvm-riscv
> 
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