From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.skyhub.de ([78.46.96.112]:34901 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755035AbbI0KP1 (ORCPT ); Sun, 27 Sep 2015 06:15:27 -0400 Date: Sun, 27 Sep 2015 12:40:14 +0200 From: Borislav Petkov To: Ingo Molnar Cc: Ard Biesheuvel , Matt Fleming , Thomas Gleixner , "H. Peter Anvin" , "linux-kernel@vger.kernel.org" , "linux-efi@vger.kernel.org" , Leif Lindholm , Catalin Marinas , Will Deacon , "stable@vger.kernel.org" , Matt Fleming , Mark Rutland , Mark Salter , Linus Torvalds , Andrew Morton , Andy Lutomirski , Denys Vlasenko , Brian Gerst Subject: Re: [PATCH 2/2] arm64/efi: Don't pad between EFI_MEMORY_RUNTIME regions Message-ID: <20150927104014.GA7631@pd.tnic> References: <1443218539-7610-1-git-send-email-matt@codeblueprint.co.uk> <1443218539-7610-3-git-send-email-matt@codeblueprint.co.uk> <20150926060159.GB25877@gmail.com> <20150927070644.GC26125@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20150927070644.GC26125@gmail.com> Sender: stable-owner@vger.kernel.org List-ID: On Sun, Sep 27, 2015 at 09:06:44AM +0200, Ingo Molnar wrote: > Could we please re-list all the arguments pro and contra of 1:1 physical mappings, > in a post that also explains the background so that more people can chime in, not > just people versed in EFI internals? It's very much possible that a bad decision > was made. The main reason why we did the additional, top-down mapping was kexec kernel wanting to use UEFI runtime facilities too and the braindead design of SetVirtualAddressMap() being callable only once per system boot. So we had to have stable mappings which are valid in the kexec-ed kernel too. But this was long time ago and I most certainly have forgotten all the details. And now I'm wondering why didn't we do the 1:1 thing and rebuild the exact same EFI pagetable in the kexec-ed kernel? Because when we do an EFI call, we switch to the special pagetable so why didn't we make the kexec-ed kernel rebuild the 1:1 pagetable which it can use for EFI calls... Hmm, again, I've forgotten a lot of details so I'm sure Matt will come in and say "No, you can't do that because..." -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply.