linux-kernel - Re: [RFC v1 0/8] x86/init: Linux linker tables

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Message-ID: <CAB=NE6W7C+QRP569gNscKustam64ULjXjmH-ey7KGn9ZZCEX_w@mail.gmail.com>
Date:	Thu, 17 Dec 2015 15:58:41 -0800
From:	"Luis R. Rodriguez" <mcgrof@...not-panic.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	"Luis R. Rodriguez" <mcgrof@...not-panic.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Andy Lutomirski <luto@...capital.net>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>, mcb30@...e.org,
	Juergen Gross <jgross@...e.com>,
	Jan Beulich <JBeulich@...e.com>, joro@...tes.org,
	Andrey Ryabinin <ryabinin.a.a@...il.com>,
	andreyknvl@...gle.com, long.wanglong@...wei.com,
	qiuxishi@...wei.com, aryabinin@...tuozzo.com,
	Mauro Carvalho Chehab <mchehab@....samsung.com>,
	Valentin Rothberg <valentinrothberg@...il.com>,
	Peter Senna Tschudin <peter.senna@...il.com>,
	X86 ML <x86@...nel.org>, Michal Marek <mmarek@...e.com>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	Michael Matz <matz@...e.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC v1 0/8] x86/init: Linux linker tables

On Thu, Dec 17, 2015 at 3:46 PM, Luis R. Rodriguez <mcgrof@...e.com> wrote:
> solutions such
> as those devised on the IOMMU init stuff do memmove() for sorting depending on
> semantics defined (in the simplest case here so far dependency between init
> sequences), this makes each set of sequences very subsystem specific

I should also note -- since the sort uses memmove() we're constrained
to using run time sort only once we can ensure the kernel can do that
without issues. I'd hope x86_64_start_reservations() is a safe place,
if not please let me know. Likewise, since one prospect here is to
bring further strong subarchitecture semantics even earlier (help
appreciated), say as early as possible in x86_64_start_kernel(), it'd
be nice to know the earliest memmove() is safe there.

In this case the solution doesn't yet make use of calls in between
x86_64_start_kernel() and  x86_64_start_reservations() but if it could
(we'd need a way for x86_init_fn_early_init() to access the
subarchitecture, help appreciated) we *might* in the future want run
time sort this early. It might still be possible to *not* do a run
time sort until later so long as the priority level linker sort
mechanism suffices for all early init routines. That's another
possibility, should memmove() be a problem that early.

 Luis
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