From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752434AbdLLKcm convert rfc822-to-8bit (ORCPT ); Tue, 12 Dec 2017 05:32:42 -0500 Received: from prv-mh.provo.novell.com ([137.65.248.74]:43255 "EHLO prv-mh.provo.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751956AbdLLKci (ORCPT ); Tue, 12 Dec 2017 05:32:38 -0500 Message-Id: <5A2FBE540200007800196B52@prv-mh.provo.novell.com> X-Mailer: Novell GroupWise Internet Agent 14.2.2 Date: Tue, 12 Dec 2017 03:32:36 -0700 From: "Jan Beulich" To: "Boris Ostrovsky" , "Juergen Gross" Cc: , , "xen-devel" , , Subject: [PATCH 2/2] x86-64/Xen: eliminate W+X mappings References: <5A2FBC570200007800196B3E@prv-mh.provo.novell.com> In-Reply-To: <5A2FBC570200007800196B3E@prv-mh.provo.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org A few thousand such pages are usually left around due to the re-use of L1 tables having been provided by the hypervisor (Dom0) or tool stack (DomU). Set NX in the direct map variant, which needs to be done in L2 due to the dual use of the re-used L1s. For x86_configure_nx() to actually do what it is supposed to do, call get_cpu_cap() first. This was broken by commit 4763ed4d45 ("x86, mm: Clean up and simplify NX enablement") when switching away from the direct EFER read. Signed-off-by: Jan Beulich --- While I certainly dislike the added header inclusion to obtain the prototype for get_cpu_cap(), I couldn't find a better alternative. I'm open to suggestions. --- arch/x86/xen/enlighten_pv.c | 3 +++ arch/x86/xen/mmu_pv.c | 10 ++++++++++ 2 files changed, 13 insertions(+) --- 4.15-rc3/arch/x86/xen/enlighten_pv.c +++ 4.15-rc3-x86_64-Xen-avoid-W+X/arch/x86/xen/enlighten_pv.c @@ -88,6 +88,8 @@ #include "multicalls.h" #include "pmu.h" +#include "../kernel/cpu/cpu.h" /* get_cpu_cap() */ + void *xen_initial_gdt; static int xen_cpu_up_prepare_pv(unsigned int cpu); @@ -1258,6 +1260,7 @@ asmlinkage __visible void __init xen_sta __userpte_alloc_gfp &= ~__GFP_HIGHMEM; /* Work out if we support NX */ + get_cpu_cap(&boot_cpu_data); x86_configure_nx(); /* Get mfn list */ --- 4.15-rc3/arch/x86/xen/mmu_pv.c +++ 4.15-rc3-x86_64-Xen-avoid-W+X/arch/x86/xen/mmu_pv.c @@ -1902,6 +1902,16 @@ void __init xen_setup_kernel_pagetable(p /* Graft it onto L4[511][510] */ copy_page(level2_kernel_pgt, l2); + /* Zap execute permission from the ident map. Due to the sharing of + * L1 entries we need to do this in the L2. */ + if (__supported_pte_mask & _PAGE_NX) + for (i = 0; i < PTRS_PER_PMD; ++i) { + if (pmd_none(level2_ident_pgt[i])) + continue; + level2_ident_pgt[i] = + pmd_set_flags(level2_ident_pgt[i], _PAGE_NX); + } + /* Copy the initial P->M table mappings if necessary. */ i = pgd_index(xen_start_info->mfn_list); if (i && i < pgd_index(__START_KERNEL_map))