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From: "H. Peter Anvin" <hpa@zytor.com>
To: Linus Torvalds <torvalds@linux-foundation.org>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: the arch/x86 maintainers <x86@kernel.org>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Dave Hansen <dave.hansen@intel.com>,
	Andy Lutomirski <luto@kernel.org>, Borislav Petkov <bp@suse.de>,
	linux-mm <linux-mm@kvack.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [RFC 0/3] x86: Patchable constants
Date: Wed, 7 Feb 2018 12:43:33 -0800	[thread overview]
Message-ID: <83ddad10-936f-9848-e3d1-8c6e73ab2969@zytor.com> (raw)
In-Reply-To: <8fea57cc-8772-f8b4-3298-91b0de126358@zytor.com>

FYI: the interface I'm implementing looks like this:

	[output =] const_op(data, variable);

... where variable can be any variable with a static address, although
in any sane scenario it should be __ro_after_init.  During
initialization, it kicks out to an out-of-line (.alternatives_aux)
handler which accesses the variable in normal fashion, but at
alternatives-patching time it inlines the relevant opcodes.

Some of the assembly infrastructure for this is indeed hairy, especially
when the out-of-line hander needs temp registers.

	-hpa

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      reply	other threads:[~2018-02-07 20:50 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-02-07 14:59 Kirill A. Shutemov
2018-02-07 14:59 ` [RFC 1/3] x86: Introduce patchable constants Kirill A. Shutemov
2018-02-07 14:59 ` [RFC 2/3] x86/mm/encrypt: Convert __PHYSICAL_MASK to patchable constant Kirill A. Shutemov
2018-02-07 14:59 ` [RFC 3/3] x86/mm/encrypt: Convert sme_me_mask " Kirill A. Shutemov
2018-02-07 16:25 ` [RFC 0/3] x86: Patchable constants Peter Zijlstra
2018-02-07 17:12   ` Kirill A. Shutemov
2018-02-07 17:01 ` Linus Torvalds
2018-02-07 17:13   ` hpa
2018-02-07 20:20   ` H. Peter Anvin
2018-02-07 20:43     ` H. Peter Anvin [this message]

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