lkml.org 
[lkml]   [2020]   [Nov]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v6 17/17] RFC: mm: add mmu_notifier argument to follow_pfn
On Fri, Nov 20, 2020 at 02:30:29PM -0400, Jason Gunthorpe wrote:
> On Thu, Nov 19, 2020 at 03:41:46PM +0100, Daniel Vetter wrote:
> > @@ -4805,21 +4824,15 @@ EXPORT_SYMBOL(follow_pte_pmd);
> > * Return: zero and the pfn at @pfn on success, -ve otherwise.
> > */
> > int follow_pfn(struct vm_area_struct *vma, unsigned long address,
> > - unsigned long *pfn)
> > + unsigned long *pfn, struct mmu_notifier *subscription)
> > {
> > - int ret = -EINVAL;
> > - spinlock_t *ptl;
> > - pte_t *ptep;
> > + if (WARN_ON(!subscription->mm))
> > + return -EINVAL;
> >
> > + if (WARN_ON(subscription->mm != vma->vm_mm))
> > + return -EINVAL;
>
> These two things are redundant right? vma->vm_mm != NULL?

Yup, will remove.

> BTW, why do we even have this for nommu? If the only caller is kvm,
> can you even compile kvm on nommu??

Kinda makes sense, but I have no idea how to make sure with compile
testing this is really the case. And I didn't see any hard evidence in
Kconfig or Makefile that mmu notifiers requires CONFIG_MMU. So not sure
what to do here.

Should I just remove the nommu version of follow_pfn and see what happens?
We can't remove it earlier since it's still used by other subsystems.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

\
 
 \ /
  Last update: 2020-11-24 15:29    [W:0.286 / U:1.128 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site