Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.37 as permitted sender) client-ip=23.128.96.37;
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>
In-Reply-To: <CAHk-=wiALZxieQQmvv5sW15HYB_YwC3d_ma9sdp7Zb4Fb4uK2w@mail.gmail.com>
From:   Uros Bizjak <ubizjak@gmail.com>
Date:   Tue, 10 Oct 2023 20:41:29 +0200
Message-ID: <CAFULd4Y8NSArDqH=VMy8F97eNosUUGxrBMEyHH=MytjUBSCmjg@mail.gmail.com>
Subject: Re: [PATCH v2 -tip] x86/percpu: Use C for arch_raw_cpu_ptr()
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     x86@kernel.org, linux-kernel@vger.kernel.org,
        Nadav Amit <namit@vmware.com>,
        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>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Tue, Oct 10, 2023 at 8:38=E2=80=AFPM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> On Tue, 10 Oct 2023 at 11:22, Uros Bizjak <ubizjak@gmail.com> wrote:
> >
> > Please note that besides propagation of the addition into address, the
> > patch also exposes memory load to the compiler, with the anticipation
> > that the compiler CSEs the load from this_cpu_off from eventual
> > multiple addresses. For this to work, we have to get rid of the asms.
>
> I actually checked that the inline asm gets combined, the same way the
> this_cpu_read_stable cases do (which we use for 'current').

Yes, but does it CSE the load from multiple addresses?

Uros.