From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it0-f71.google.com (mail-it0-f71.google.com [209.85.214.71]) by kanga.kvack.org (Postfix) with ESMTP id B4BDE6B0279 for ; Thu, 1 Jun 2017 09:59:26 -0400 (EDT) Received: by mail-it0-f71.google.com with SMTP id n13so41592596ita.7 for ; Thu, 01 Jun 2017 06:59:26 -0700 (PDT) Received: from mail.kernel.org (mail.kernel.org. [198.145.29.99]) by mx.google.com with ESMTPS id l26si28723811pli.24.2017.06.01.06.59.25 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 01 Jun 2017 06:59:26 -0700 (PDT) Received: from mail-ua0-f182.google.com (mail-ua0-f182.google.com [209.85.217.182]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 8EF3A2395B for ; Thu, 1 Jun 2017 13:59:25 +0000 (UTC) Received: by mail-ua0-f182.google.com with SMTP id x47so27939163uab.0 for ; Thu, 01 Jun 2017 06:59:25 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20170531150349.4816-1-jglisse@redhat.com> References: <20170531150349.4816-1-jglisse@redhat.com> From: Andy Lutomirski Date: Thu, 1 Jun 2017 06:59:04 -0700 Message-ID: Subject: Re: [PATCH] x86/mm: do not BUG_ON() on stall pgd entries Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= Cc: "linux-mm@kvack.org" , Ingo Molnar , "Kirill A . Shutemov" On Wed, May 31, 2017 at 8:03 AM, J=C3=A9r=C3=B4me Glisse wrote: > Since af2cf278ef4f ("Don't remove PGD entries in remove_pagetable()") > we no longer cleanup stall pgd entries and thus the BUG_ON() inside > sync_global_pgds() is wrong. > > This patch remove the BUG_ON() and unconditionaly update stall pgd > entries. > > Signed-off-by: J=C3=A9r=C3=B4me Glisse > Cc: Ingo Molnar > Cc: Kirill A. Shutemov > --- > arch/x86/mm/init_64.c | 7 +------ > 1 file changed, 1 insertion(+), 6 deletions(-) > > diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c > index ff95fe8..36b9020 100644 > --- a/arch/x86/mm/init_64.c > +++ b/arch/x86/mm/init_64.c > @@ -123,12 +123,7 @@ void sync_global_pgds(unsigned long start, unsigned = long end) > pgt_lock =3D &pgd_page_get_mm(page)->page_table_l= ock; > spin_lock(pgt_lock); > > - if (!p4d_none(*p4d_ref) && !p4d_none(*p4d)) > - BUG_ON(p4d_page_vaddr(*p4d) > - !=3D p4d_page_vaddr(*p4d_ref)); > - > - if (p4d_none(*p4d)) > - set_p4d(p4d, *p4d_ref); > + set_p4d(p4d, *p4d_ref); If we have a mismatch in the vmalloc range, vmalloc_fault is going to screw up and we'll end up using incorrect page tables. What's causing the mismatch? If you're hitting this BUG in practice, I suspect we have a bug elsewhere. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org