linux-kernel - Re: [PATCH v2] arch/cacheflush: Introduce flush_all

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Date:   Mon, 22 Aug 2022 06:37:36 -0700
From:   Davidlohr Bueso <dave@...olabs.net>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     linux-arch@...r.kernel.org, dan.j.williams@...el.com,
        peterz@...radead.org, mark.rutland@....com, dave.jiang@...el.com,
        Jonathan.Cameron@...wei.com, a.manzanares@...sung.com,
        bwidawsk@...nel.org, alison.schofield@...el.com,
        ira.weiny@...el.com, linux-cxl@...r.kernel.org,
        nvdimm@...ts.linux.dev, x86@...nel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] arch/cacheflush: Introduce flush_all_caches()

On Sun, 21 Aug 2022, Christoph Hellwig wrote:

>On Fri, Aug 19, 2022 at 10:10:24AM -0700, Davidlohr Bueso wrote:
>> index b192d917a6d0..ac4d4fd4e508 100644
>> --- a/arch/x86/include/asm/cacheflush.h
>> +++ b/arch/x86/include/asm/cacheflush.h
>> @@ -10,4 +10,8 @@
>>
>>  void clflush_cache_range(void *addr, unsigned int size);
>>
>> +/* see comments in the stub version */
>> +#define flush_all_caches() \
>> +	do { wbinvd_on_all_cpus(); } while(0)
>
>Yikes.  This is just a horrible, horrible name and placement for a bad
>hack that should have no generic relevance.

Why does this have no generic relevance? There's already been discussions
on how much wbinv is hated[0].

>Please fix up the naming to make it clear that this function is for a
>very specific nvdimm use case, and move it to a nvdimm-specific header
>file.

Do you have any suggestions for a name? And, as the changelog describes,
this is not nvdimm specific anymore, and the whole point of all this is
volatile memory components for cxl, hence nvdimm namespace is bogus.

[0] https://lore.kernel.org/all/Yvtc2u1J%2Fqip8za9@worktop.programming.kicks-ass.net/

Thanks,
Davidlohr