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Date:      Mon, 10 Jan 2022 14:14:54 -0700
From:      Warner Losh <imp@bsdimp.com>
To:        John Baldwin <jhb@freebsd.org>
Cc:        Warner Losh <imp@freebsd.org>, src-committers <src-committers@freebsd.org>,  "<dev-commits-src-all@freebsd.org>" <dev-commits-src-all@freebsd.org>, dev-commits-src-main@freebsd.org
Subject:   Re: git: d6c0538dae8d - main - ddb: Remove SOFTWARE_SSTEP support
Message-ID:  <CANCZdfq0UCZvdcsuaWx3KXqrKBBYoxDHqc=_P3U7L4QpCyh=rw@mail.gmail.com>
In-Reply-To: <45275428-75e2-aaae-bed3-e5e84b39e17c@FreeBSD.org>
References:  <202201071627.207GRsGX062055@gitrepo.freebsd.org> <45275428-75e2-aaae-bed3-e5e84b39e17c@FreeBSD.org>

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On Mon, Jan 10, 2022 at 12:48 PM John Baldwin <jhb@freebsd.org> wrote:

> On 1/7/22 8:27 AM, Warner Losh wrote:
> > The branch main has been updated by imp:
> >
> > URL:
> https://cgit.FreeBSD.org/src/commit/?id=d6c0538dae8d138219dfd051994a44c50e741212
> >
> > commit d6c0538dae8d138219dfd051994a44c50e741212
> > Author:     Warner Losh <imp@FreeBSD.org>
> > AuthorDate: 2022-01-07 16:25:33 +0000
> > Commit:     Warner Losh <imp@FreeBSD.org>
> > CommitDate: 2022-01-07 16:25:33 +0000
> >
> >      ddb: Remove SOFTWARE_SSTEP support
> >
> >      It was needed for mips only, and only kinda sorta worked for mips.
> It
> >      can be brought back if we grow another architecture that need it.
> >
> >      Sponsored by:           Netflix
>
> RISC-V would need it in theory (no hardware single step), but no one has
> felt the
> need to implement the backend support for it.  I think 32-bit arm doesn't
> support
> hardware single step either (but again, no one has bothered to add the
> backend
> support).
>

Generally, I agree with these thoughts. I went ahead with the removal
because I
knew it would be easy to bring back, even years from now should someone[tm]
have an implementation for those platforms (though I thought 32-bit arm did
have
single step in hardware).

Should I put it back? Or should we wait until someone shows up with support
for
a supported platform?

Warner

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<div dir=3D"ltr"><div dir=3D"ltr"><br></div><br><div class=3D"gmail_quote">=
<div dir=3D"ltr" class=3D"gmail_attr">On Mon, Jan 10, 2022 at 12:48 PM John=
 Baldwin &lt;<a href=3D"mailto:jhb@freebsd.org">jhb@freebsd.org</a>&gt; wro=
te:<br></div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px =
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">On 1/7/22 8:=
27 AM, Warner Losh wrote:<br>
&gt; The branch main has been updated by imp:<br>
&gt; <br>
&gt; URL: <a href=3D"https://cgit.FreeBSD.org/src/commit/?id=3Dd6c0538dae8d=
138219dfd051994a44c50e741212" rel=3D"noreferrer" target=3D"_blank">https://=
cgit.FreeBSD.org/src/commit/?id=3Dd6c0538dae8d138219dfd051994a44c50e741212<=
/a><br>
&gt; <br>
&gt; commit d6c0538dae8d138219dfd051994a44c50e741212<br>
&gt; Author:=C2=A0 =C2=A0 =C2=A0Warner Losh &lt;imp@FreeBSD.org&gt;<br>
&gt; AuthorDate: 2022-01-07 16:25:33 +0000<br>
&gt; Commit:=C2=A0 =C2=A0 =C2=A0Warner Losh &lt;imp@FreeBSD.org&gt;<br>
&gt; CommitDate: 2022-01-07 16:25:33 +0000<br>
&gt; <br>
&gt;=C2=A0 =C2=A0 =C2=A0 ddb: Remove SOFTWARE_SSTEP support<br>
&gt;=C2=A0 =C2=A0 =C2=A0 <br>
&gt;=C2=A0 =C2=A0 =C2=A0 It was needed for mips only, and only kinda sorta =
worked for mips. It<br>
&gt;=C2=A0 =C2=A0 =C2=A0 can be brought back if we grow another architectur=
e that need it.<br>
&gt;=C2=A0 =C2=A0 =C2=A0 <br>
&gt;=C2=A0 =C2=A0 =C2=A0 Sponsored by:=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =
=C2=A0Netflix<br>
<br>
RISC-V would need it in theory (no hardware single step), but no one has fe=
lt the<br>
need to implement the backend support for it.=C2=A0 I think 32-bit arm does=
n&#39;t support<br>
hardware single step either (but again, no one has bothered to add the back=
end<br>
support).<br></blockquote><div><br></div><div>Generally, I agree with these=
 thoughts. I went ahead with the removal because I</div><div>knew it would =
be easy to bring back, even years from now should someone[tm]</div><div>hav=
e an implementation for those platforms (though I thought 32-bit arm did ha=
ve</div><div>single step in hardware).</div><div><br></div><div>Should I pu=
t it back? Or should we wait until someone shows up with support for</div><=
div>a supported platform?</div><div><br></div><div>Warner</div></div></div>

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