Re: [PATCH v5] um: switch to regset API and depend on XSTATE

[SeongJae Park <sj@kernel.org>]

On Tue, 03 Dec 2024 18:07:36 +0100 Benjamin Berg <benjamin@sipsolutions.net> wrote:

> On Tue, 2024-12-03 at 07:56 -0800, SeongJae Park wrote:
> > On Tue, 03 Dec 2024 07:01:09 SeongJae Park <sj@kernel.org> wrote:
> > 
> > > On Tue, 03 Dec 2024 09:40:34 +0100 Benjamin Berg
> > > <benjamin@sipsolutions.net> wrote:
> > > 
> > > > Hi,
> > > > 
> > > > that probably means the size detection for the FPU state (i.e.
> > > > PTRACE_GETREGSET for NT_X86_XSTATE is incorrect on a 32bit host
> > > > in some
> > > > way.
> > > > 
> > > > Is there anything special about the qemu setup or it is just a
> > > > default
> > > > qemu-x86?
> > > 
> > > I use default qemu-system-x86_64 on my system.
> > > 
> > >     $ qemu-system-x86_64 --version
> > >     QEMU emulator version 8.2.2 (qemu-8.2.2-1.1.hs+fb.el9)
> > >     Copyright (c) 2003-2023 Fabrice Bellard and the QEMU Project
> > > developers
> > > 
> > > I forgot saying it is not just x86 but x86_64, sorry.
> > 
> > Oh, and seems my qemu has some downstream changes.  I will try to reproduce the
> > issue with upstream versions and report the result again.
> 
> I doubt that is the reason. The code tries to detect the size of the
> NT_X86_XSTATE register set and something breaks.
> 
> Thinking about it a bit, the only good explanation is that the qemu CPU
> does not have XSTATE support. This would cause the ptrace syscall to
> fetch the NT_X86_XSTATE register set to always fail (with -ENODEV).
> 
> Honestly, I just had not expected such an issue. Could you try the
> below patch to add a fallback?

Thank you, I just confiremd it fixes my issue.

Tested-by: SeongJae Park <sj@kernel.org>


Thanks,
SJ

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