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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Wed, 4 Oct 2023 13:12:40 -0700
Message-ID: <CAHk-=whKc9UCsrZ6sNRb=T2Yhy4Dhr=LUBi9r-gPhfwCmuOeZA@mail.gmail.com>
Subject: Re: [PATCH v2 4/4] x86/percpu: Use C for percpu read/write accessors
To:     Uros Bizjak <ubizjak@gmail.com>
Cc:     x86@kernel.org, linux-kernel@vger.kernel.org,
        Andy Lutomirski <luto@kernel.org>,
        Ingo Molnar <mingo@kernel.org>, Nadav Amit <namit@vmware.com>,
        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>,
        Borislav Petkov <bp@alien8.de>,
        Josh Poimboeuf <jpoimboe@redhat.com>
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On Wed, 4 Oct 2023 at 13:08, Uros Bizjak <ubizjak@gmail.com> wrote:
>
> You get a store forwarding stall when you write a bigger operand to
> memory and then read part of it, if the smaller part doesn't start at
> the same address.

I don't think that has been true for over a decade now.

Afaik, any half-way modern Intel and AMD cores will forward any fully
contained load.

The whole "same address" was a P4 thing, iirc.

          Linus