Re: [PATCH 1/1] gdb, gdbserver: Add Intel APX register support

[Keith Seitz <keiths@redhat.com>]

Hi,

On 7/25/26 3:53 AM, Christina Joos wrote:
> From: "H.J. Lu" <hjl.tools@gmail.com>
> 
> Intel Advanced Performance Extensions (APX) doubles the number of
> general-purpose registers (GPRs) from 16 to 32 (r16-r31).

Thank you for pursuing this. I'm not going to claim that I completely
understand the nuiance of modern x86_64 features, but generally,
the code seems okay to me.

> Those new 64-bit Extended GPRs (EGPRs) do not change the size of the
> XSAVE area, as they take up the space left behind by the deprecated
> MPX registers.
> 
> In contrast to the legacy GPRS, EGPRs are not enabled by default in 64-bit
> mode but are xcr0 enabled based on APX_F Intel APX state.  Define
> X86_XSTATE_APX_F to support this new configuration.
> 
> Add gdb and gdbserver registers support for those new 64-bit EGPRs.
> Also add byte, word and dword pseudo register support.

I appreciate the simplified approach in this revision, removing the
previously proposed maint commands. Generating core files is much
better/safe approach.

One trivial nit (no need to repost):
I previously asked whether apx_offset should be set independently of
PKRU/AVX512 in i387_guess_xsave_layout()[1]. You explained that APX is
only expected with PKRU or AVX512 on known Intel CPUs addresses[2].

A brief comment documenting that assumption would be helpful for future 
readers. 'Cause, as expected, I forgot all about that discussion
already! :-p

Reviewed-By: Keith Seitz <keiths@redhat.com>

Keith

[1] https://sourceware.org/pipermail/gdb-patches/2026-June/228135.html
[2] https://sourceware.org/pipermail/gdb-patches/2026-July/228491.html