Re: [PATCH v2] rust: page: add byte-wise atomic memory copy methods

[Alice Ryhl]

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