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Date: Wed, 29 Nov 2017 12:58:15 -0800
From: Andi Kleen <ak@linux.intel.com>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Thomas Gleixner <tglx@linutronix.de>, Borislav Petkov <bp@suse.de>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Ingo Molnar <mingo@redhat.com>, x86@kernel.org,
        "H. Peter Anvin" <hpa@zytor.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andy Lutomirski <luto@amacapital.net>,
        Cyrill Gorcunov <gorcunov@openvz.org>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCHv2 0/4] x86: 5-level related changes into decompression
 code
Message-ID: <20171129205815.GE3070@tassilo.jf.intel.com>
References: <20171110220645.59944-1-kirill.shutemov@linux.intel.com>
 <20171129154908.6y4st6xc7hbsey2v@pd.tnic>
 <20171129161349.d7ksuhwhdamloty6@node.shutemov.name>
 <alpine.DEB.2.20.1711291740050.1825@nanos>
 <20171129170831.2iqpop2u534mgrbc@node.shutemov.name>
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> We're really early in the boot -- startup_64 in decompression code -- and
> I don't know a way print a message there. Is there a way?
> 
> no_longmode handled by just hanging the machine. Is it enough for no_la57
> case too?

The way to handle it is to check it early in the real mode boot code when you 
can still print messages. That is how missing long mode is handled.

-Andi