Re: [PATCH v6 0/7] x86/fpu: Restore and reinforce signal frame portability

[Andrei Vagin]

On Wed, Sep 16, 2026 at 4:27 PM Andrei Vagin <avagin@xxxxxxxxxx> wrote:
>
> The x86 signal frame is designed to be self-describing. The xstate_size
> field in the software-reserved bytes indicates the actual size of the
> xstate context and is used by the kernel to locate the FP_XSTATE_MAGIC2
> marker during signal return.
>
> This design is required to provide portability of signal frames across
> different machines. For example, a process checkpointed on a system with
> fewer xstate features and restored on a system with more features will
> have a signal frame on its stack that is smaller than the destination
> host's default. By relying on the frame's internal xstate_size, the
> kernel can correctly validate and restore such frames.
>
> This series restores and improves signal frame portability. The goal is
> to allow process migration across CPUs with heterogeneous FPU
> capabilities, as long as the process only uses features supported by
> both systems. This version addresses the original issues by pre-faulting
> only the required size of the xstate buffer (rather than the default
> task size), and includes cleanups requested by Ingo Molnar.
>
> v6:
>   - Clarify struct _fpstate_32 layout and reformat documentation per
>     Borislav comments.
>   - Add Reviewed-by tags from Chang S. Bae.

Sashiko reported no issues, all patches are green:
https://sashiko.dev/#/patchset/20260916232310.490786-1-avagin%40google.com

I think this series is ready to merge. Thanks to everyone involved.

Thanks,
Andrei