Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756817AbbKEWcT (ORCPT ); Thu, 5 Nov 2015 17:32:19 -0500 Received: from terminus.zytor.com ([198.137.202.10]:40609 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752296AbbKEWcS (ORCPT ); Thu, 5 Nov 2015 17:32:18 -0500 Subject: Re: [PATCH] x86/mm: Skip the hypervisor range when walking PGD To: Boris Ostrovsky , tglx@linutronix.de, mingo@redhat.com References: <1446749795-27764-1-git-send-email-boris.ostrovsky@oracle.com> Cc: x86@kernel.org, linux-kernel@vger.kernel.org, linux@eikelenboom.it, xen-devel@lists.xen.org From: "H. Peter Anvin" Message-ID: <563BD8D6.107@zytor.com> Date: Thu, 5 Nov 2015 14:31:50 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: <1446749795-27764-1-git-send-email-boris.ostrovsky@oracle.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2213 Lines: 55 On 11/05/15 10:56, Boris Ostrovsky wrote: > The range between 0xffff800000000000 and 0xffff87ffffffffff is reserved > for hypervisor and therefore we should not try to follow PGD's indexes > corresponding to those addresses. > > While this has alsways been a problem, with commit e1a58320a38d ("x86/mm: > Warn on W^X mappings") ptdump_walk_pgd_level_core() can now be called > during boot, causing a PV Xen guest to crash. > > Reported-by: Sander Eikelenboom > Signed-off-by: Boris Ostrovsky > --- > arch/x86/mm/dump_pagetables.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c > index 1bf417e..756c921 100644 > --- a/arch/x86/mm/dump_pagetables.c > +++ b/arch/x86/mm/dump_pagetables.c > @@ -362,8 +362,13 @@ static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd, > bool checkwx) > { > #ifdef CONFIG_X86_64 > +/* ffff800000000000 - ffff87ffffffffff is reserved for hypervisor */ > +#define is_hypervisor_range(idx) (paravirt_enabled() && \ > + (((idx) >= pgd_index(__PAGE_OFFSET) - 16) && \ > + ((idx) < pgd_index(__PAGE_OFFSET)))) > pgd_t *start = (pgd_t *) &init_level4_pgt; > #else > +#define is_hypervisor_range(idx) 0 > pgd_t *start = swapper_pg_dir; > #endif > pgprotval_t prot; > @@ -381,7 +386,7 @@ static void ptdump_walk_pgd_level_core(struct seq_file *m, pgd_t *pgd, > > for (i = 0; i < PTRS_PER_PGD; i++) { > st.current_address = normalize_addr(i * PGD_LEVEL_MULT); > - if (!pgd_none(*start)) { > + if (!pgd_none(*start) && !is_hypervisor_range(i)) { > if (pgd_large(*start) || !pgd_present(*start)) { > prot = pgd_flags(*start); > note_page(m, &st, __pgprot(prot), 1); > Maybe we could use the max_lines field in the address_markers[] array? We really shouldn't be mapping anything in the hypervisor space even on native. -hpa -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/