Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:6 as permitted sender) client-ip=2620:137:e000::3:6;
MIME-Version: 1.0
References: <20231010164234.140750-1-ubizjak@gmail.com> <CAHk-=whYWhZN52SJN-Th9x2L2V-vHtAXUgiy_nSJ3+vQU6ak4Q@mail.gmail.com>
 <CAFULd4ZqH3FeG8_mjDvUAU9QiGB36wDu3MzUtadgAgoVuQ9QRg@mail.gmail.com>
 <CAHk-=wiALZxieQQmvv5sW15HYB_YwC3d_ma9sdp7Zb4Fb4uK2w@mail.gmail.com>
 <F48A9D34-3627-4372-B555-B58CBFC3F241@vmware.com> <CAHk-=wjF4gzCZKh-zN-sY0WpX1kCo+s9gYE9sOcSv0QieH1dwQ@mail.gmail.com>
 <CAFULd4bmOa7G2dXd_mu4J=_bsEs+TbxH691tYx9QQBwJPAma9w@mail.gmail.com>
 <CAHk-=wj2Co_g3RQ=JkDZC7PYbRqDPq7mePQ0=eYhhtpEgqJD0w@mail.gmail.com>
 <0617BB2F-D08F-410F-A6EE-4135BB03863C@vmware.com> <CAFULd4Zjd6idrLXuF59cwKxyd1a--DsiJwGQAKai9Tph30dAow@mail.gmail.com>
 <CAHk-=wgSsfo89ESHcngvPCkQSh_YAJG-0g7fupb+Uv0E1d_EcQ@mail.gmail.com>
 <7D77A452-E61E-4B8B-B49C-949E1C8E257C@vmware.com> <CAHk-=wj1dLFkL9Qv2vtk0O8Q6WE-11Jq3KucZoz2Kkw59LAexw@mail.gmail.com>
 <9F926586-20D9-4979-AB7A-71124BBAABD3@vmware.com> <CAHk-=wi7YKPKKZw5SpA9gZcf4paG4pZ2kUM50g-LQmdF0g6vWg@mail.gmail.com>
 <CAFULd4bpHkNzCzKed23mTTBWRyhPnOm91f+F6UE413VK+oFtMQ@mail.gmail.com>
 <CAFULd4Z-q4Ot6iyOLo7DkjE=dY3RHXUV+yx6R0iWk=-tZ6ufhQ@mail.gmail.com>
 <CAHk-=wjSnECwAe+Bi0PD6uods3ZDs8up5OAy-qZKF5OgPLpDiA@mail.gmail.com>
 <CAFULd4bLEU-tBC8dO1wf66UAxQ2d1HxQ=D6wvtHZfdQCKhnpkw@mail.gmail.com>
 <CAFULd4YAFTFqon3ojv7N6h=G_1pAjSH3T6YvX0G=g7Fwh7j1jQ@mail.gmail.com>
 <A2E458DE-8B84-4FB2-BF6D-3EAB2B355078@vmware.com> <CAFULd4b_PdKb=8U5+Zz-XNoYdULtcQJnmf-yCrpCv7RRogSXyQ@mail.gmail.com>
 <CAFULd4Y8_MOMGcatcMuUaC89zX5F-VYr0niiJ9Yd8hQ16neHjw@mail.gmail.com>
 <3F9D776E-AD7E-4814-9E3C-508550AD9287@vmware.com> <CAFULd4Zruoq4b5imt3NfN4D+0RY2-i==KGAwUHR8JD0T8=HJBw@mail.gmail.com>
 <28B9471C-4FB0-4AB0-81DD-4885C3645E95@vmware.com> <CAHk-=whS8-Lk_=mFp=mr-JrbRYtScgz-4s_GLAOQGafa_3zP9g@mail.gmail.com>
 <CAFULd4akMtMxk1C-NsfzYFP6rkt5QUuHACq+BFEJV6u_8n+yiA@mail.gmail.com>
In-Reply-To: <CAFULd4akMtMxk1C-NsfzYFP6rkt5QUuHACq+BFEJV6u_8n+yiA@mail.gmail.com>
From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Wed, 18 Oct 2023 11:11:24 -0700
Message-ID: <CAHk-=whm81-JmJ_ej8wPuifTOD7rF35MXjwJeGDKCR7h99Eyaw@mail.gmail.com>
Subject: Re: [PATCH v2 -tip] x86/percpu: Use C for arch_raw_cpu_ptr()
To:     Uros Bizjak <ubizjak@gmail.com>
Cc:     Nadav Amit <namit@vmware.com>,
        "the arch/x86 maintainers" <x86@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Andy Lutomirski <luto@kernel.org>,
        Brian Gerst <brgerst@gmail.com>,
        Denys Vlasenko <dvlasenk@redhat.com>,
        "H . Peter Anvin" <hpa@zytor.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Nick Desaulniers <ndesaulniers@google.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Wed, 18 Oct 2023 at 10:23, Uros Bizjak <ubizjak@gmail.com> wrote:
>
> In processor.h, we have:
>
> static __always_inline unsigned long current_top_of_stack(void)

Yeah, but that is never used multiple times afaik. I think it's purely
for things like

        WARN_ON_ONCE(!on_thread_stack());

in the entry code, for example.

So I guess it can use the same infrastructure, but I doubt it matters
in any practical way.

Grepping around for it, it looks like the 32-bit code has some stale commentary:

         * Reload esp0 and pcpu_hot.top_of_stack.  This changes
         * current_thread_info().

but that seems entirely bogus. We historically picked up
current_thread_info() from %esp, but that hasn't been true in ages,
afaik. Now it's all based on 'current'.

           Linus