Re: [PATCH v5 6/8] string: introduce memcpy_nt() helpers

["David Hildenbrand (Arm)" <david@kernel.org>]

On 7/6/26 13:53, Li Zhe wrote:
> On Mon, Jul 6, 2026 at 11:18:48AM +0200, david@kernel.org wrote:
> 
>>> +
>>> +#define __HAVE_ARCH_MEMCPY_NT 1
>>> +/*
>>> + * Reuse the existing x86 flushcache backend as the nt copy primitive.
>>> + * Callers pair it with memcpy_nt_drain() when later stores must be
>>> + * ordered after the copy.
>>> + */
>>> +static __always_inline void memcpy_nt(void *dst, const void *src, size_t cnt)
>>> +{
>>> +	memcpy_flushcache(dst, src, cnt);
>>> +}
>>
>> In particular if you end up with a single function (that jsut requires a write
>> memory barrier afterwards), please make this
>>
>> #define memcpy_nt memcpy_nt
>>
>> instead.
> 
> Thanks for the review.
> 
> Just to make sure I understood this correctly: do you mean that, rather
> than using a separate __HAVE_ARCH_MEMCPY_NT feature macro, you would
> prefer the usual self-macro override pattern, with
> 
>     #define memcpy_nt memcpy_nt
> 
> in arch/x86/include/asm/string_64.h and the generic fallback kept under
> #ifndef memcpy_nt in include/linux/string.h?

Yes, that's what Linus suggested as the preferred way for single functions when
it came up in different context recently.

-- 
Cheers,

David