Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753195AbdHODrV (ORCPT ); Mon, 14 Aug 2017 23:47:21 -0400 Received: from mail-it0-f47.google.com ([209.85.214.47]:33994 "EHLO mail-it0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752946AbdHODrU (ORCPT ); Mon, 14 Aug 2017 23:47:20 -0400 Date: Mon, 14 Aug 2017 21:47:18 -0600 From: Tycho Andersen To: Laura Abbott Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel-hardening@lists.openwall.com, Marco Benatto , Juerg Haefliger , Juerg Haefliger Subject: Re: [PATCH v5 02/10] mm, x86: Add support for eXclusive Page Frame Ownership (XPFO) Message-ID: <20170815034718.o6fej2gqkmypxtl2@smitten> References: <20170809200755.11234-1-tycho@docker.com> <20170809200755.11234-3-tycho@docker.com> <910adbb5-c5d7-3091-1c92-996f73dd6221@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <910adbb5-c5d7-3091-1c92-996f73dd6221@redhat.com> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3206 Lines: 93 Hi Laura, On Mon, Aug 14, 2017 at 03:30:00PM -0700, Laura Abbott wrote: > On 08/09/2017 01:07 PM, Tycho Andersen wrote: > > +/* Update a single kernel page table entry */ > > +inline void set_kpte(void *kaddr, struct page *page, pgprot_t prot) > > +{ > > + unsigned int level; > > + pgprot_t msk_clr; > > + pte_t *pte = lookup_address((unsigned long)kaddr, &level); > > + > > + BUG_ON(!pte); > > + > > + switch (level) { > > + case PG_LEVEL_4K: > > + set_pte_atomic(pte, pfn_pte(page_to_pfn(page), canon_pgprot(prot))); > > + break; > > + case PG_LEVEL_2M: > > + /* We need to check if it's a 2M page or 1GB page before retrieve > > + * pgprot info, as each one will be extracted from a different > > + * page table levels */ > > + msk_clr = pmd_pgprot(*(pmd_t*)pte); > > + case PG_LEVEL_1G: { > > + struct cpa_data cpa; > > + int do_split; > > + > > + msk_clr = pud_pgprot(*(pud_t*)pte); > > + > > + memset(&cpa, 0, sizeof(cpa)); > > + cpa.vaddr = kaddr; > > + cpa.pages = &page; > > + cpa.mask_set = prot; > > + cpa.mask_clr = msk_clr; > > + cpa.numpages = 1; > > + cpa.flags = 0; > > + cpa.curpage = 0; > > + cpa.force_split = 0; > > + > > + > > + do_split = try_preserve_large_page(pte, (unsigned long)kaddr, &cpa); > > + if (do_split) { > > + spin_lock(&cpa_lock); > > + BUG_ON(split_large_page(&cpa, pte, (unsigned long)kaddr)); > > + spin_unlock(&cpa_lock); > > + } > > This doesn't work in atomic contexts: > > [ 28.263571] BUG: sleeping function called from invalid context at > mm/page_alloc.c:4048 > [ 28.263575] in_atomic(): 1, irqs_disabled(): 1, pid: 2433, name: > gnome-terminal > [ 28.263576] INFO: lockdep is turned off. > [ 28.263578] irq event stamp: 0 > [ 28.263580] hardirqs last enabled at (0): [< (null)>] > (null) > [ 28.263584] hardirqs last disabled at (0): [] > copy_process.part.25+0x62a/0x1e90 > [ 28.263587] softirqs last enabled at (0): [] > copy_process.part.25+0x62a/0x1e90 > [ 28.263588] softirqs last disabled at (0): [< (null)>] > (null) > [ 28.263591] CPU: 0 PID: 2433 Comm: gnome-terminal Tainted: G W > 4.13.0-rc5-xpfo+ #86 > [ 28.263592] Hardware name: LENOVO 20BTS1N700/20BTS1N700, BIOS N14ET28W > (1.06 ) 03/12/2015 > [ 28.263593] Call Trace: > [ 28.263598] dump_stack+0x8e/0xd6 > [ 28.263601] ___might_sleep+0x164/0x250 > [ 28.263604] __might_sleep+0x4a/0x80 > [ 28.263607] __alloc_pages_nodemask+0x2b3/0x3e0 > [ 28.263611] alloc_pages_current+0x6a/0xe0 > [ 28.263614] split_large_page+0x4e/0x360 > [ 28.263618] set_kpte+0x12c/0x150 > [ 28.263623] xpfo_kunmap+0x7e/0xa0 > [ 28.263627] wp_page_copy+0x16e/0x800 > [ 28.263631] do_wp_page+0x9a/0x580 > [ 28.263633] __handle_mm_fault+0xb1c/0x1130 > [ 28.263638] handle_mm_fault+0x178/0x350 > [ 28.263641] __do_page_fault+0x26e/0x510 > [ 28.263644] do_page_fault+0x30/0x80 > [ 28.263647] page_fault+0x28/0x30 > > > split_large_page calls alloc_page with GFP_KERNEL. switching to > use GFP_ATOMIC in this path works locally for me. Oof, thanks. I'll do that for the next version, and also CC x86 in case they may have better suggestions. Cheers, Tycho