linux-kernel - Re: [PATCH V4 mm-hotfixes 1/3] mm: move page table sync declarations to linux/pgtable.h

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Message-ID: <aJmrpaeKKeNCV3G_@hyeyoo>
Date: Mon, 11 Aug 2025 17:36:53 +0900
From: Harry Yoo <harry.yoo@...cle.com>
To: Mike Rapoport <rppt@...nel.org>
Cc: Dennis Zhou <dennis@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>, x86@...nel.org,
        Borislav Petkov <bp@...en8.de>, Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
        Tejun Heo <tj@...nel.org>, Uladzislau Rezki <urezki@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Christoph Lameter <cl@...two.org>,
        David Hildenbrand <david@...hat.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        "H. Peter Anvin" <hpa@...or.com>, kasan-dev@...glegroups.com,
        Ard Biesheuvel <ardb@...nel.org>, linux-kernel@...r.kernel.org,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Alexander Potapenko <glider@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Suren Baghdasaryan <surenb@...gle.com>, Thomas Huth <thuth@...hat.com>,
        John Hubbard <jhubbard@...dia.com>,
        Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
        Michal Hocko <mhocko@...e.com>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>, linux-mm@...ck.org,
        "Kirill A. Shutemov" <kas@...nel.org>,
        Oscar Salvador <osalvador@...e.de>, Jane Chu <jane.chu@...cle.com>,
        Gwan-gyeong Mun <gwan-gyeong.mun@...el.com>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
        Joerg Roedel <joro@...tes.org>, Alistair Popple <apopple@...dia.com>,
        Joao Martins <joao.m.martins@...cle.com>, linux-arch@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH V4 mm-hotfixes 1/3] mm: move page table sync declarations
 to linux/pgtable.h

On Mon, Aug 11, 2025 at 11:05:51AM +0300, Mike Rapoport wrote:
> On Mon, Aug 11, 2025 at 02:34:18PM +0900, Harry Yoo wrote:
> > Move ARCH_PAGE_TABLE_SYNC_MASK and arch_sync_kernel_mappings() to
> > linux/pgtable.h so that they can be used outside of vmalloc and ioremap.
> > 
> > Cc: <stable@...r.kernel.org>
> > Fixes: 8d400913c231 ("x86/vmemmap: handle unpopulated sub-pmd ranges")
> > Signed-off-by: Harry Yoo <harry.yoo@...cle.com>
> > ---
> >  include/linux/pgtable.h | 16 ++++++++++++++++
> >  include/linux/vmalloc.h | 16 ----------------
> >  2 files changed, 16 insertions(+), 16 deletions(-)
> > 
> > diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
> > index 4c035637eeb7..ba699df6ef69 100644
> > --- a/include/linux/pgtable.h
> > +++ b/include/linux/pgtable.h
> > @@ -1467,6 +1467,22 @@ static inline void modify_prot_commit_ptes(struct vm_area_struct *vma, unsigned
> >  }
> >  #endif
> >  
> > +/*
> > + * Architectures can set this mask to a combination of PGTBL_P?D_MODIFIED values
> > + * and let generic vmalloc and ioremap code know when arch_sync_kernel_mappings()
> 
> If ARCH_PAGE_TABLE_SYNC_MASK can be used outside vmalloc(), the comment
> needs an update, maybe
> 
> ... and let the generic code that modifies kernel page tables

Right, and patch 2 updates the comment as it uses it outside vmalloc():

diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index ba699df6ef69..0cf5c6c3e483 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -1469,8 +1469,8 @@ static inline void modify_prot_commit_ptes(struct vm_area_struct *vma, unsigned

 /*
  * Architectures can set this mask to a combination of PGTBL_P?D_MODIFIED values
- * and let generic vmalloc and ioremap code know when arch_sync_kernel_mappings()
- * needs to be called.
+ * and let generic vmalloc, ioremap and page table update code know when
+ * arch_sync_kernel_mappings() needs to be called.
  */
 #ifndef ARCH_PAGE_TABLE_SYNC_MASK
 #define ARCH_PAGE_TABLE_SYNC_MASK 0

Or if you think "page table update code" is unclear, please let me know.

> Other than that
> 
> Reviewed-by: Mike Rapoport (Microsoft) <rppt@...nel.org>

Thanks a lot for all the reviews, Mike!

-- 
Cheers,
Harry / Hyeonggon