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

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Date:   Tue, 16 Aug 2022 11:01:14 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Davidlohr Bueso <dave@...olabs.net>
Cc:     Dan Williams <dan.j.williams@...el.com>,
        Mark Rutland <mark.rutland@....com>,
        Dave Jiang <dave.jiang@...el.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        linux-cxl@...r.kernel.org, nvdimm@...ts.linux.dev,
        bwidawsk@...nel.org, ira.weiny@...el.com, vishal.l.verma@...el.com,
        alison.schofield@...el.com, a.manzanares@...sung.com,
        linux-arch@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
        linux-arm-kernel@...ts.infradead.org, bp@...en8.de, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arch/cacheflush: Introduce flush_all_caches()

On Mon, Aug 15, 2022 at 09:07:06AM -0700, Davidlohr Bueso wrote:
> diff --git a/arch/x86/include/asm/cacheflush.h b/arch/x86/include/asm/cacheflush.h
> index b192d917a6d0..ce2ec9556093 100644
> --- a/arch/x86/include/asm/cacheflush.h
> +++ b/arch/x86/include/asm/cacheflush.h
> @@ -10,4 +10,7 @@
> 
>  void clflush_cache_range(void *addr, unsigned int size);
> 
> +#define flush_all_caches() \
> +	do { wbinvd_on_all_cpus(); } while(0)
> +

This is horrific... we've done our utmost best to remove all WBINVD
usage and here you're adding it back in the most horrible form possible
?!?

Please don't do this, do *NOT* use WBINVD.