Re: [PATCH] coroutine: add libucontext as external library

[Joelle van Dyne]

On Tue, Mar 9, 2021 at 1:36 AM Daniel P. Berrangé <berrange@redhat.com> wrote:
>
> On Mon, Mar 08, 2021 at 07:26:36PM -0800, Joelle van Dyne wrote:
> > iOS does not support ucontext natively for aarch64 and the sigaltstack is
> > also unsupported (even worse, it fails silently, see:
> > https://openradar.appspot.com/13002712 )
> >
> > As a workaround we include a library implementation of ucontext and add it
> > as a build option.
>
> The README here:
>
>   https://github.com/kaniini/libucontext
>
> indicates that it is intentionally limiting what registers it saves
> and restores, explicitly excluding FPU.
>
> Peter & Paolo expressed concern about this, indicating FPU reg support
> was a requirement for QEMU:
>
>    https://lists.gnu.org/archive/html/qemu-devel/2021-01/msg05525.html
>
Does it make a difference if this is provided as an option and not as
a replacement? Would it make sense to add some warning at configure
time? Right now none of the concurrency backends are supported on iOS
and it's possible support will go away on macOS as well in the future.
QEMU would not be able to run at all.

-j

> Regards,
> Daniel
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