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Date: Fri, 8 Dec 2017 12:28:42 +0100
From: Ingo Molnar <mingo@kernel.org>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Ingo Molnar <mingo@redhat.com>, x86@kernel.org,
        Thomas Gleixner <tglx@linutronix.de>, "H. Peter Anvin" <hpa@zytor.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andy Lutomirski <luto@amacapital.net>,
        Cyrill Gorcunov <gorcunov@openvz.org>, Borislav Petkov <bp@suse.de>,
        Andi Kleen <ak@linux.intel.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCHv4 3/4] x86/boot/compressed/64: Introduce
 place_trampoline()
Message-ID: <20171208112842.jfh4rnu3nzdab4o6@gmail.com>
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* Kirill A. Shutemov <kirill@shutemov.name> wrote:

> On Thu, Dec 07, 2017 at 07:30:48AM +0100, Ingo Molnar wrote:
> > > We also need a small stack in the trampoline to re-enable long mode via
> > > long return. But stack and code can share the page just fine.
> > 
> > BTW., I'm not sure this is necessarily a good idea: it means writable+executable 
> > memory, which we generally try to avoid. How complicated would it be to have them 
> > separate?
> 
> It's trivial: you only need to bump TRAMPOLINE_32BIT_SIZE.
> 
> But it doesn't make much sense. We're running from indentity mapping: all
> memory is r/w without NX bit set (and IA32_EFER.NXE is 0).

Ok, fair enough!

Thanks,

	Ingo