From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f197.google.com (mail-wr0-f197.google.com [209.85.128.197]) by kanga.kvack.org (Postfix) with ESMTP id 20E046B0292 for ; Wed, 7 Jun 2017 14:17:10 -0400 (EDT) Received: by mail-wr0-f197.google.com with SMTP id z70so2374440wrc.1 for ; Wed, 07 Jun 2017 11:17:10 -0700 (PDT) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id k44sor449363eda.3.2017.06.07.11.17.08 for (Google Transport Security); Wed, 07 Jun 2017 11:17:08 -0700 (PDT) Date: Wed, 7 Jun 2017 21:17:06 +0300 From: "Kirill A. Shutemov" Subject: Re: [PATCH] x86/mm/hotplug: fix BUG_ON() after hotremove by not freeing pud v2 Message-ID: <20170607181705.7jortbns732jtiba@node.shutemov.name> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1169495863.31360420.1496857080560.JavaMail.zimbra@redhat.com> Sender: owner-linux-mm@kvack.org List-ID: To: Jerome Glisse Cc: "Kirill A. Shutemov" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andy Lutomirski , Ingo Molnar , Logan Gunthorpe 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: Jerome 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: Jerome 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. -- Kirill A. Shutemov -- 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