Re: [PATCH 0/3] linux-user: Call tcg_flush_jmp_cache() before re-using threads

[Philippe Mathieu-Daudé]

Hi Ilya,

ping? :)

On 2/1/25 19:25, Philippe Mathieu-Daudé wrote:
> Fix a bug reported by Ilya in:
> https://lore.kernel.org/qemu-devel/uuuk6a2vo24yrrqrchjxaeko3utqshrdu6txcnqziokpg7dkom@4l4kd3dqh6jc/
>
> Commit bb6cf6f0168 ("accel/tcg: Factor tcg_cpu_reset_hold()
> out") wanted to restrict tlb_flush() to system emulation,
> but inadvertently also restricted tcg_flush_jmp_cache(),
> which was before called on user emulation via:
>
>    Realize -> Reset -> cpu_common_reset_hold()
>
> Since threads (vCPUs) use a common CPUJumpCache, when many
> threads are created / joined, they eventually end re-using
> a CPUJumpCache entry, which was cleared when the first vCPU
> was allocated (via Realize) but then stayed dirty.
>
> Have cpu_exec_reset_hold() call the common tcg_exec_reset()
> helper on user emulation, eventually calling tcg_flush_jmp_cache().
>
> Philippe Mathieu-Daudé (3):
>    linux-user: Only include 'exec/tb-flush.h' header when necessary
>    accel/tcg: Factor out common tcg_exec_reset() helper
>    accel/tcg: Implement cpu_exec_reset_hold() on user emulation
>
>   accel/tcg/internal-common.h | 1 +
>   linux-user/user-internals.h | 1 -
>   accel/tcg/cpu-exec-common.c | 6 ++++++
>   accel/tcg/tcg-accel-ops.c   | 4 ++--
>   accel/tcg/user-exec-stub.c  | 4 ----
>   accel/tcg/user-exec.c       | 5 +++++
>   linux-user/mmap.c           | 1 +
>   linux-user/syscall.c        | 1 +
>   8 files changed, 16 insertions(+), 7 deletions(-)