Date: Mon, 8 Apr 2024 22:31:17 +0200 From: Warner Losh <imp@bsdimp.com> To: Paul Floyd <pjfloyd@wanadoo.fr> Cc: freebsd-arm@freebsd.org Subject: Re: arm64 mrs and system registers Message-ID: <CANCZdfpQBTWK-8DTR0TwE8LzPe81EQ7LzwZpw54iQeAs9d7Fvw@mail.gmail.com> In-Reply-To: <e7aa2897-e05a-4a91-a1a0-f6c0a03156ae@wanadoo.fr> References: <e7aa2897-e05a-4a91-a1a0-f6c0a03156ae@wanadoo.fr>
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--000000000000b3f6b806159bb09b Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Mon, Apr 8, 2024 at 9:03=E2=80=AFPM Paul Floyd <pjfloyd@wanadoo.fr> wrot= e: > Hi > > I've been looking at this bugzilla item > > https://bugs.kde.org/show_bug.cgi?id=3D392146 > > Is there any difference between Linux and FreeBSD when it comes to what > registers and fields are exposed by the kernel (see comment 17 in the > link above). > I don't think so. We've not seen issues with other drivers on aarch64 excep= t when they were written on x86 and didn't have the synchronization needed for the weaker memory models in aarch64 systems. > I did have a poke around the kernel code but it's a bit hard to tell > exactly which of the access macros are being used, without exhaustively > grepping for them one by one. > Yea, I think that there's missing atomics on the state transitions and/or some missing locking that "magically" provides barriers that make it work on x86. Warner --000000000000b3f6b806159bb09b Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable <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, Apr 8, 2024 at 9:03=E2=80=AFP= M Paul Floyd <<a href=3D"mailto:pjfloyd@wanadoo.fr">pjfloyd@wanadoo.fr</= a>> wrote:<br></div><blockquote class=3D"gmail_quote" style=3D"margin:0p= x 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Hi= <br> <br> I've been looking at this bugzilla item<br> <br> <a href=3D"https://bugs.kde.org/show_bug.cgi?id=3D392146" rel=3D"noreferrer= " target=3D"_blank">https://bugs.kde.org/show_bug.cgi?id=3D392146</a><br>; <br> Is there any difference between Linux and FreeBSD when it comes to what <br= > registers and fields are exposed by the kernel (see comment 17 in the <br> link above).<br></blockquote><div><br></div><div>I don't think so. We&#= 39;ve not seen issues with other drivers on aarch64 except</div><div>when t= hey were written on x86 and didn't have the synchronization needed</div= ><div>for the weaker memory models in aarch64 systems.</div><div>=C2=A0</di= v><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;borde= r-left:1px solid rgb(204,204,204);padding-left:1ex"> I did have a poke around the kernel code but it's a bit hard to tell <b= r> exactly which of the access macros are being used, without exhaustively <br= > grepping for them one by one.<br></blockquote><div><br></div><div>Yea, I th= ink that there's missing atomics on the state transitions and/or</div><= div>some missing locking that "magically" provides barriers that = make it work</div><div>on x86.</div><div><br></div><div>Warner=C2=A0</div><= /div></div> --000000000000b3f6b806159bb09b--
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