linux-kernel - Re: [PATCH] perf: map pages in advance

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20241129122624.GH24400@noisy.programming.kicks-ass.net>
Date: Fri, 29 Nov 2024 13:26:24 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: David Hildenbrand <david@...hat.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Kan Liang <kan.liang@...ux.intel.com>,
	linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, Matthew Wilcox <willy@...radead.org>
Subject: Re: [PATCH] perf: map pages in advance

On Fri, Nov 29, 2024 at 01:12:57PM +0100, David Hildenbrand wrote:

> Well, I think we simply will want vm_insert_pages_prot() that stops treating
> these things like folios :) . *likely*  we'd want a distinct memdesc/type.
> 
> We could start that work right now by making some user (iouring,
> ring_buffer) set a new page->_type, and checking that in
> vm_insert_pages_prot() + vm_normal_page(). If set, don't touch the refcount
> and the mapcount.
> 
> Because then, we can just make all the relevant drivers set the type, refuse
> in vm_insert_pages_prot() anything that doesn't have the type set, and
> refuse in vm_normal_page() any pages with this memdesc.
> 
> Maybe we'd have to teach CoW to copy from such pages, maybe not. GUP of
> these things will stop working, I hope that is not a problem.

Well... perf-tool likes to call write() upon these pages in order to
write out the data from the mmap() into a file.