From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754899AbdFWTsL (ORCPT ); Fri, 23 Jun 2017 15:48:11 -0400 Received: from mx1.redhat.com ([209.132.183.28]:57208 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754781AbdFWTsK (ORCPT ); Fri, 23 Jun 2017 15:48:10 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com B670B8F231 Authentication-Results: ext-mx02.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx02.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=jglisse@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com B670B8F231 Date: Fri, 23 Jun 2017 15:48:05 -0400 From: Jerome Glisse To: akpm@linux-foundation.org Cc: "Kirill A. Shutemov" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andy Lutomirski , Ingo Molnar , Logan Gunthorpe Subject: Re: [PATCH] x86/mm/hotplug: fix BUG_ON() after hotremove by not freeing pud v2 Message-ID: <20170623194805.GD3128@redhat.com> References: <1496846780-17393-1-git-send-email-jglisse@redhat.com> <20170607170325.65ex46hoqjalprnu@black.fi.intel.com> <20170607170651.exful7yvxvrjaolz@node.shutemov.name> <1169495863.31360420.1496857080560.JavaMail.zimbra@redhat.com> <20170607181705.7jortbns732jtiba@node.shutemov.name> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20170607181705.7jortbns732jtiba@node.shutemov.name> User-Agent: Mutt/1.8.3 (2017-05-23) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Fri, 23 Jun 2017 19:48:10 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 07, 2017 at 09:17:06PM +0300, Kirill A. Shutemov wrote: > On Wed, Jun 07, 2017 at 01:38:00PM -0400, Jerome Glisse wrote: > > > On Wed, Jun 07, 2017 at 08:03:25PM +0300, Kirill A. Shutemov wrote: > > > > On Wed, Jun 07, 2017 at 10:46:20AM -0400, jglisse@redhat.com wrote: > > > > > From: Jérôme Glisse > > > > > > > > > > With commit af2cf278ef4f we no longer free pud so that we do not > > > > > have synchronize all pgd on hotremove/vfree. But the new 5 level > > > > > page table patchset reverted that for 4 level page table. > > > > > > > > > > This patch restore af2cf278ef4f and disable free_pud() if we are > > > > > in the 4 level page table case thus avoiding BUG_ON() after hot- > > > > > remove. > > > > > > > > > > af2cf278ef4f x86/mm/hotplug: Don't remove PGD entries in > > > > > remove_pagetable() > > > > > > > > > > Changed since v1: > > > > > - make free_pud() conditional on the number of page table > > > > > level > > > > > - improved commit message > > > > > > > > > > Signed-off-by: Jérôme Glisse > > > > > Cc: Andy Lutomirski > > > > > Cc: Ingo Molnar > > > > > Cc: Kirill A. Shutemov > > > > > Cc: Logan Gunthorpe > > > > > > thus we now trigger a BUG_ON() l128 in sync_global_pgds() > > > > > > > > > > > > This patch remove free_pud() like in af2cf278ef4f > > > > > --- > > > > > arch/x86/mm/init_64.c | 11 +++++++++++ > > > > > 1 file changed, 11 insertions(+) > > > > > > > > > > diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c > > > > > index 95651dc..61028bc 100644 > > > > > --- a/arch/x86/mm/init_64.c > > > > > +++ b/arch/x86/mm/init_64.c > > > > > @@ -771,6 +771,16 @@ static void __meminit free_pmd_table(pmd_t > > > > > *pmd_start, pud_t *pud) > > > > > spin_unlock(&init_mm.page_table_lock); > > > > > } > > > > > > > > > > +/* > > > > > + * For 4 levels page table we do not want to free puds but for 5 levels > > > > > + * we should free them. This code also need to change to adapt for boot > > > > > + * time switching between 4 and 5 level. > > > > > + */ > > > > > +#if CONFIG_PGTABLE_LEVELS == 4 > > > > > +static inline void free_pud_table(pud_t *pud_start, p4d_t *p4d) > > > > > +{ > > > > > +} > > > > > > > > Just "if (CONFIG_PGTABLE_LEVELS > 4)" before calling free_pud_table(), but > > > > okay -- I'll rework it anyway for boot-time switching. > > > > > > Err. "if (CONFIG_PGTABLE_LEVELS == 4)" obviously. > > > > You want me to respawn a v3 or is that good enough until you finish > > boot time 5 level page table ? > > It doesn't matter for me. Upto Ingo. Andrew any news on this ? This fix a regression in 4.12 so it would be nice to have this fix or similar in. I can repost a v3 without inline ie directly ifdefing the callsite. Note that Kyrill will rework that but i think this is 4.13 material. Cheers, Jérôme