From: Peter Zijlstra <peterz@infradead.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Steven Rostedt <rostedt@goodmis.org>,
LKML <linux-kernel@vger.kernel.org>,
"x86@kernel.org" <x86@kernel.org>,
Linux Trace Kernel <linux-trace-kernel@vger.kernel.org>,
Kees Cook <keescook@chromium.org>,
Dave Hansen <dave.hansen@intel.com>,
Sean Christopherson <seanjc@google.com>,
linux-arch@vger.kernel.org
Subject: Re: [RFC PATCH] text_poke/ftrace/x86: Allow text_poke() to be called in early boot
Date: Tue, 25 Oct 2022 12:28:56 +0200 [thread overview]
Message-ID: <Y1e6aOmOfXrSOB/u@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <CAHk-=wji4q7rGUWDLonnEnxq0ykNCcYGpMrNnZg89rAwOgyRKg@mail.gmail.com>
On Mon, Oct 24, 2022 at 05:11:13PM -0700, Linus Torvalds wrote:
> All of this comes from "poking_init()" being a steaming pile of bovine
> excrement, doing random odd things, and having that special
> "copy_init_mm()" helper that just makes things even worse. Nothing
> else uses that, and it shouldn't have called "dup_mm()" in the first
> place.
Agreed; dup_mm() makes no sense and it is easily removed, see my earlier
patch. Perhaps it can be simplified further to:
__poking_mm = init_mm
omitting the mm_init() I retained, but I need to stare harder at all
that.
> I'm not even sure why "poking_mm" exists at all, and why it has
> created a whole new copy of "init_mm", and why this code isn't just
> using '&init_mm' like everything else that wants to just walk the
> kernel page tables.
Because it instantiates user-space page-tables in it, you really don't
want those in init_mm.
The whole (and sole) purpose of poking_mm is to contain the writable
aliases. Only the CPU that has the poking_mm active has access to them.
prev parent reply other threads:[~2022-10-25 10:30 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-24 23:03 [RFC PATCH] text_poke/ftrace/x86: Allow text_poke() to be called in early boot Steven Rostedt
2022-10-25 0:11 ` Linus Torvalds
2022-10-25 0:21 ` Steven Rostedt
2022-10-25 1:02 ` Linus Torvalds
2022-10-25 1:05 ` Steven Rostedt
2022-10-25 1:06 ` Linus Torvalds
2022-10-25 10:28 ` Peter Zijlstra [this message]
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