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

Harry Yoo
2025-08-11T08:37:42Z

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@vger.kernel.org>
> > Fixes: 8d400913c231 ("x86/vmemmap: handle unpopulated sub-pmd ranges")
> > Signed-off-by: Harry Yoo <harry.yoo@oracle.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@kernel.org>

Thanks a lot for all the reviews, Mike!

--
Cheers,
Harry / Hyeonggon