lkml.org 
[lkml]   [2020]   [Nov]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v5 05/15] mm/frame-vector: Use FOLL_LONGTERM
On Wed, Nov 04, 2020 at 04:37:58PM +0000, Christoph Hellwig wrote:
> On Wed, Nov 04, 2020 at 05:26:58PM +0100, Daniel Vetter wrote:
> > What we're discussing is whether gup_fast and pup_fast also obey this,
> > or fall over and can give you the struct page that's backing the
> > dma_mmap_* memory. Since the _fast variant doesn't check for
> > vma->vm_flags, and afaict that's the only thing which closes this gap.
> > And like you restate, that would be a bit a problem. So where's that
> > check which Jason&me aren't spotting?
>
> remap_pte_range uses pte_mkspecial to set up the PTEs, and gup_pte_range
> errors out on pte_special. Of course this only works for the
> CONFIG_ARCH_HAS_PTE_SPECIAL case, for other architectures we do have
> a real problem.

Except that we don't really support pte-level gup-fast without
CONFIG_ARCH_HAS_PTE_SPECIAL, and in fact all architectures selecting
HAVE_FAST_GUP also select ARCH_HAS_PTE_SPECIAL, so we should be fine.

\
 
 \ /
  Last update: 2020-11-04 17:41    [W:0.441 / U:0.012 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site