linux-kernel - Re: [PATCH v5 3/4] tracing: Use vmap_page

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Message-ID: <CAHk-=wifCDa6FfRKzeioYuEqJFTeXnYQ1DpeuYsmmn59NWuakQ@mail.gmail.com>
Date: Wed, 2 Apr 2025 09:42:00 -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>, 
	Jann Horn <jannh@...gle.com>
Subject: Re: [PATCH v5 3/4] tracing: Use vmap_page_range() to map memmap ring buffer

On Tue, 1 Apr 2025 at 15:57, Steven Rostedt <rostedt@...dmis.org> wrote:
>
> The code to map the physical memory retrieved by memmap currently
> allocates an array of pages to cover the physical memory and then calls
> vmap() to map it to a virtual address. Instead of using this temporary
> array of struct page descriptors, simply use vmap_page_range() that can
> directly map the contiguous physical memory to a virtual address.

Wait, what?

Didn't you just say that you can just use page_address() for the kernel mapping?

So the whole vmap thing is entirely unnecessary in the first place.

Including the simpler vmap_page_range().

             Linus