Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753125AbeAEV3y (ORCPT + 1 other); Fri, 5 Jan 2018 16:29:54 -0500 Received: from mail-pl0-f66.google.com ([209.85.160.66]:34443 "EHLO mail-pl0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753031AbeAEV3x (ORCPT ); Fri, 5 Jan 2018 16:29:53 -0500 X-Google-Smtp-Source: ACJfBov8cHHkfJkfv7rVkRZLg0jrIC/7tWNajBzS2iqpwnWXLsQoFK3SDctj1pjaw4EHDv/C7immQg== Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (1.0) Subject: Re: [PATCH 05/23] x86, kaiser: unmap kernel from userspace page tables (core patch) From: Andy Lutomirski X-Mailer: iPhone Mail (15C153) In-Reply-To: Date: Fri, 5 Jan 2018 13:29:50 -0800 Cc: Dave Hansen , Yisheng Xie , linux-kernel@vger.kernel.org, linux-mm@kvack.org, richard.fellner@student.tugraz.at, moritz.lipp@iaik.tugraz.at, daniel.gruss@iaik.tugraz.at, michael.schwarz@iaik.tugraz.at, luto@kernel.org, Linus Torvalds , keescook@google.com, hughd@google.com, x86@kernel.org, Andrea Arcangeli Content-Transfer-Encoding: 8BIT Message-Id: References: <20171123003438.48A0EEDE@viggo.jf.intel.com> <20171123003447.1DB395E3@viggo.jf.intel.com> <93776eb2-b6d4-679a-280c-8ba558a69c34@linux.intel.com> <20a54a5f-f4e5-2126-fb73-6a995d13d52d@linux.intel.com> <282e2a56-ded1-6eb9-5ecb-22858c424bd7@linux.intel.com> <868196c9-52ed-4270-968f-97b7a6784f61@linux.intel.com> To: Jiri Kosina Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: > On Jan 5, 2018, at 1:14 PM, Jiri Kosina wrote: > > On Fri, 5 Jan 2018, Dave Hansen wrote: > >>>>> --- a/arch/x86/platform/efi/efi_64.c >>>>> +++ b/arch/x86/platform/efi/efi_64.c >>>>> @@ -95,6 +95,12 @@ pgd_t * __init efi_call_phys_prolog(void >>>>> save_pgd[pgd] = *pgd_offset_k(pgd * PGDIR_SIZE); >>>>> vaddress = (unsigned long)__va(pgd * PGDIR_SIZE); >>>>> set_pgd(pgd_offset_k(pgd * PGDIR_SIZE), *pgd_offset_k(vaddress)); >>>>> + /* >>>>> + * pgprot API doesn't clear it for PGD >>>>> + * >>>>> + * Will be brought back automatically in _epilog() >>>>> + */ >>>>> + pgd_offset_k(pgd * PGDIR_SIZE)->pgd &= ~_PAGE_NX; >>>>> } >>>>> __flush_tlb_all(); >>>> >>>> Wait a sec... Where does the _PAGE_USER come from? Shouldn't we see >>>> the &init_mm in there and *not* set _PAGE_USER? >>> >>> That's because pgd_populate() uses _PAGE_TABLE and not _KERNPG_TABLE for >>> reasons that are behind me. >>> >>> I did put this on my TODO list, but for later. >>> >>> (and yes, I tried clearing _PAGE_USER from init_mm's PGD, and no obvious >>> breakages appeared, but I wanted to give it more thought later). >> >> Feel free to add my Ack on this. > > Thanks. I'll extract the patch out of this thread and submit it > separately, so that it doesn't get lost buried here. > >> I'd personally much rather muck with random relatively unused bits of >> the efi code than touch the core PGD code. > > Exactly. Especially at this point. > >> We need to go look at it again in the 4.16 timeframe, probably. > > Agreed. On my TODO list already. Can we just delete the old memmap code instead? --Andy >