linux-kernel - Re: [PATCH v6 3/4] tracing: Use vmap_page

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Message-ID: <4f8ece8b-8862-4f7c-8ede-febd28f8a9fe@roeck-us.net>
Date: Sun, 6 Apr 2025 10:39:27 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.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 v6 3/4] tracing: Use vmap_page_range() to map memmap ring
 buffer

On Wed, Apr 02, 2025 at 10:49:06AM -0400, Steven Rostedt wrote:
> From: Steven Rostedt <rostedt@...dmis.org>
> 
> 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.
> 
> Link: https://lore.kernel.org/all/CAHk-=whUOfVucfJRt7E0AH+GV41ELmS4wJqxHDnui6Giddfkzw@mail.gmail.com/
> 
> Suggested-by: Linus Torvalds <torvalds@...ux-foundation.org>
> Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
> ---
>  kernel/trace/trace.c | 33 ++++++++++++++++-----------------
...
> +	area = get_vm_area(size, VM_IOREMAP);

non-MMU builds (xtensa:nommu_kc705_defconfig):

kernel/trace/trace.o:(.init.literal+0x250): undefined reference to `get_vm_area'

Guenter