linux-kernel - Re: [PATCH v2 1/2] tracing: ring-buffer: Have the ring buffer code do the vmap of physical memory

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Message-ID: <CAHk-=wh4b8hNT5XRDj9M4damUmij2bJGaRamqQ_icEkVUv8svg@mail.gmail.com>
Date: Mon, 31 Mar 2025 17:49:07 -0700
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org, 
	Masami Hiramatsu <mhiramat@...nel.org>, Mark Rutland <mark.rutland@....com>, 
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, Andrew Morton <akpm@...ux-foundation.org>, 
	Vincent Donnefort <vdonnefort@...gle.com>, Vlastimil Babka <vbabka@...e.cz>, Mike Rapoport <rppt@...nel.org>, 
	Kees Cook <kees@...nel.org>, Tony Luck <tony.luck@...el.com>, 
	"Guilherme G. Piccoli" <gpiccoli@...lia.com>, linux-hardening@...r.kernel.org, 
	Matthew Wilcox <willy@...radead.org>
Subject: Re: [PATCH v2 1/2] tracing: ring-buffer: Have the ring buffer code do
 the vmap of physical memory

 On Mon, 31 Mar 2025 at 17:38, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> So *this* is the kind of "bad in a different way" I could imagine:
> things that probably should be cleaned up and be available to generic
> code, but very few people have cared, and so they are used in ad-hoc
> places and haven't been sufficiently generalized and cleaned up.

Of course, the good news is that (a) few people care - which is why we
are in this situation - and (b) the people who *do* care about these
issues tend to be both responsible and responsive.

So not some unfixable morass, more of a "one or two architectures may
care, and we might have to extend interfaces that haven't been used
this way before".

For example, just adding flush_dcache_range() into
include/asm-generic/cacheflush.h should be more-or-less trivial, with
the same kinds of "architectures can make clear they have their own
optimized version".

              Linus