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 90E6F6B0279 for ; Wed, 7 Jun 2017 13:06:55 -0400 (EDT) Received: by mail-wr0-f197.google.com with SMTP id g36so2193462wrg.4 for ; Wed, 07 Jun 2017 10:06:55 -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 i44sor422124eda.9.2017.06.07.10.06.53 for (Google Transport Security); Wed, 07 Jun 2017 10:06:53 -0700 (PDT) Date: Wed, 7 Jun 2017 20:06:51 +0300 From: "Kirill A. Shutemov" Subject: Re: [PATCH] x86/mm/hotplug: fix BUG_ON() after hotremove by not freeing pud v2 Message-ID: <20170607170651.exful7yvxvrjaolz@node.shutemov.name> References: <1496846780-17393-1-git-send-email-jglisse@redhat.com> <20170607170325.65ex46hoqjalprnu@black.fi.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20170607170325.65ex46hoqjalprnu@black.fi.intel.com> Sender: owner-linux-mm@kvack.org List-ID: To: "Kirill A. Shutemov" Cc: jglisse@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andy Lutomirski , Ingo Molnar , Logan Gunthorpe 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. -- 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