linux-kernel - Re: [PATCH v5 0/9] riscv: vector: misc ptrace fixes for debug use-cases

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Message-ID: <CAFTtA3PDoysu+RyvH+a_ZZ4xCbGrgeYY8Xu=zFqQ__grhWGCtQ@mail.gmail.com>
Date: Wed, 21 Jan 2026 15:47:35 -0600
From: Andy Chiu <andybnac@...il.com>
To: Sergey Matyukevich <geomatsi@...il.com>
Cc: linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	linux-kselftest@...r.kernel.org, Paul Walmsley <pjw@...nel.org>, 
	Palmer Dabbelt <palmer@...belt.com>, Alexandre Ghiti <alex@...ti.fr>, Oleg Nesterov <oleg@...hat.com>, 
	Shuah Khan <shuah@...nel.org>, Thomas Huth <thuth@...hat.com>, 
	Charlie Jenkins <charlie@...osinc.com>, Samuel Holland <samuel.holland@...ive.com>, 
	Joel Granados <joel.granados@...nel.org>, Conor Dooley <conor.dooley@...rochip.com>, 
	Yong-Xuan Wang <yongxuan.wang@...ive.com>, Heiko Stuebner <heiko@...ech.de>, Guo Ren <guoren@...nel.org>
Subject: Re: [PATCH v5 0/9] riscv: vector: misc ptrace fixes for debug use-cases

Hi Sergey,

On Sun, Dec 14, 2025 at 10:35 AM Sergey Matyukevich <geomatsi@...il.com> wrote:
>
> This patch series suggests fixes for several corner cases in the RISC-V
> vector ptrace implementation:
>
> - init vector context with proper vlenb, to avoid reading zero vlenb
>   by an early attached debugger
>
> - follow gdbserver expectations and return ENODATA instead of EINVAL
>   if vector extension is supported but not yet activated for the
>   traced process
>
> - validate input vector csr registers in ptrace, to maintain an accurate
>   view of the tracee's vector context across multiple halt/resume
>   debug cycles
>
> For detailed description see the appropriate commit messages. A new test
> suite validate_v_ptrace is added to the tools/testing/selftests/riscv/vector
> to verify some of the vector ptrace functionality and corner cases.
>
> So far tested on the following platforms:
> - test in QEMU rv32/rv64
> - test on c908 (BananaPi CanMV K230D Zero)
> - test on c906 (MangoPi MQ Pro)
>
> Previous versions:
> - v4: https://lore.kernel.org/linux-riscv/20251108194207.1257866-1-geomatsi@gmail.com/T/#u
> - v3: https://lore.kernel.org/linux-riscv/20251025210655.43099-1-geomatsi@gmail.com/T/#u
> - v2: https://lore.kernel.org/linux-riscv/20250821173957.563472-1-geomatsi@gmail.com/T/#u
> - v1: https://lore.kernel.org/linux-riscv/20251007115840.2320557-1-geomatsi@gmail.com/T/#u
>
> Changes in v5:
> - add support and minimal set of tests for XTheadVector
>
> Changes in v4:
> The form 'vsetvli x0, x0, ...' can only be used if VLMAX remains
> unchanged, see spec 6.2. This condition was not met by the initial
> values in the selftests w.r.t. the initial zeroed context. QEMU accepted
> such values, but actual hardware (c908, BananaPi CanMV Zero board) did
> not, setting vill. So fix the selftests after testing on hardware:
> - replace 'vsetvli x0, x0, ...' by 'vsetvli rd, x0, ...'
> - fixed instruction returns VLMAX, so use it in checks as well
> - replace fixed vlenb == 16 in the syscall test
>
> Changes in v3:
> Address the review comments by Andy Chiu and rework the approach:
> - drop forced vector context save entirely
> - perform strict validation of vector csr regs in ptrace
>
> Changes in v2:
> - add thread_info flag to allow to force vector context save
> - force vector context save after vector ptrace to ensure valid vector
>   context in the next ptrace operations
> - force vector context save on the first context switch after vector
>   context init to get proper vlenb
>
> ---
>
> Ilya Mamay (1):
>   riscv: ptrace: return ENODATA for inactive vector extension
>
> Sergey Matyukevich (8):
>   riscv: vector: init vector context with proper vlenb
>   riscv: csr: define vtype register elements
>   riscv: ptrace: validate input vector csr registers
>   selftests: riscv: test ptrace vector interface
>   selftests: riscv: verify initial vector state with ptrace
>   selftests: riscv: verify syscalls discard vector context
>   selftests: riscv: verify ptrace rejects invalid vector csr inputs
>   selftests: riscv: verify ptrace accepts valid vector csr values
>
>  arch/riscv/include/asm/csr.h                  |  17 +
>  arch/riscv/kernel/ptrace.c                    |  98 +-
>  arch/riscv/kernel/vector.c                    |  12 +-
>  .../testing/selftests/riscv/vector/.gitignore |   2 +
>  tools/testing/selftests/riscv/vector/Makefile |  10 +-
>  .../selftests/riscv/vector/v_helpers.c        |  23 +
>  .../selftests/riscv/vector/v_helpers.h        |   2 +
>  .../riscv/vector/validate_v_ptrace.c          | 919 ++++++++++++++++++
>  8 files changed, 1075 insertions(+), 8 deletions(-)
>  create mode 100644 tools/testing/selftests/riscv/vector/validate_v_ptrace.c
>
>
> base-commit: 8f0b4cce4481fb22653697cced8d0d04027cb1e8
> --
> 2.52.0
>

For the series:

Tested-by: Andy Chiu <andybnac@...il.com>
(on qemu rv64gcv)

Thanks,
Andy