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AJvYcCUZzUBzevi6CyEd27WCzfyqoT/bigOodYBIMHtPRGNtfCgUU+UN3y9pqqzDQtwDzhmlL0t7AkjUTw==@kvack.org X-Gm-Message-State: AOJu0YzcrtoSikYljRtWQQSSCt/g/NN+AD0kz+izCR3+O62/30tNK6+j C2mkbgAsM+pVrvzNW5jD+0TdDiTafRuHFdGexX0qwUf+dt7kycGeBU+Qs4osqJ1EmDY8LWFVtxx b1Ic9qvS5sqkNjDJ0FQ== X-Received: from wmbz20.prod.google.com ([2002:a05:600c:c094:b0:47b:d5ad:dd7f]) (user=aliceryhl job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:820d:b0:47d:403e:4eaf with SMTP id 5b1f17b1804b1-48379b9f278mr197567615e9.10.1771320822308; Tue, 17 Feb 2026 01:33:42 -0800 (PST) Date: Tue, 17 Feb 2026 09:33:40 +0000 In-Reply-To: <20260217091348.GT1395266@noisy.programming.kicks-ass.net> Mime-Version: 1.0 References: <877bsgu7fb.fsf@kernel.org> <2026021313-embody-deprive-9da5@gregkh> <873434u3yq.fsf@kernel.org> <20260213142608.GV2995752@noisy.programming.kicks-ass.net> <2026021311-shorten-veal-532c@gregkh> <2026021326-stark-coastline-c5bc@gregkh> <20260217091348.GT1395266@noisy.programming.kicks-ass.net> Message-ID: Subject: Re: [PATCH v2] rust: page: add byte-wise atomic memory copy methods From: Alice Ryhl To: Peter Zijlstra Cc: Boqun Feng , Greg KH , Andreas Hindborg , Lorenzo Stoakes , "Liam R. Howlett" , Miguel Ojeda , Boqun Feng , Gary Guo , "=?utf-8?B?QmrDtnJu?= Roy Baron" , Benno Lossin , Trevor Gross , Danilo Krummrich , Will Deacon , Mark Rutland , linux-mm@kvack.org, rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" X-Rspamd-Queue-Id: 2B1FF140007 X-Stat-Signature: x643xkd7nsy9jumkhp4i7dwzprxqterk X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1771320823-952066 X-HE-Meta: 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 +pEyenFI 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Feb 17, 2026 at 10:13:48AM +0100, Peter Zijlstra wrote: > On Fri, Feb 13, 2026 at 08:19:17AM -0800, Boqun Feng wrote: > > Well, in standard C, technically memcpy() has the same problem as Rust's > > `core::ptr::copy()` and `core::ptr::copy_nonoverlapping()`, i.e. they > > are vulnerable to data races. Our in-kernel memcpy() on the other hand > > doesn't have this problem. Why? Because it's volatile byte-wise atomic > > per the implementation. > > Look at arch/x86/lib/memcpy_64.S, plenty of movq variants there. Not > byte-wise. movq is a valid implementation of 8 byte-wise copies. > Also, not a single atomic operation in sight. Relaxed atomics are just mov ops. Alice