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Howlett" , Miguel Ojeda , Boqun Feng , Gary Guo , =?iso-8859-1?Q?Bj=F6rn?= 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 Subject: Re: [PATCH v2] rust: page: add byte-wise atomic memory copy methods Message-ID: <20260217091348.GT1395266@noisy.programming.kicks-ass.net> References: <2026021343-germicide-baritone-efe8@gregkh> <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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: yx4mezwwxjt6cutnzcaj1pmjgo5q1jst X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: CF1E680008 X-HE-Tag: 1771319635-203201 X-HE-Meta: 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 aVx46Kid 49+D4e8h/5DxpcTUCkvjuCtIsw68ZFCjQw7RZqKIHbsk/IP5qcfLnYRVo7qCfkG18SqklFqZSz2D6eGLuoELdQpdz/fwRcDXL0Rkgq4ePvy4FnX8M5M9W0oBt25rpzsJyCs2dBClfSeIrHfS36Q5yJbSeR9MKqI6X0Mor/uGQcHSFvLvX0wMaDeXijKsTJhmPE5+w2+08Lm1nZRKwYihvW94btwe0UA/bFcbfvoKGbSaEtq3cd7upUwXmMumju+VR0gc6oxzAuyWVwtSmjZ9RabnVGTQpRNcJFP2O 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 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. Also, not a single atomic operation in sight.