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From: Daniel Vetter <daniel@ffwll.ch>
To: Jason Gunthorpe <jgg@ziepe.ca>
Cc: linux-samsung-soc <linux-samsung-soc@vger.kernel.org>,
	"Jan Kara" <jack@suse.cz>, "Kees Cook" <keescook@chromium.org>,
	"KVM list" <kvm@vger.kernel.org>,
	"John Hubbard" <jhubbard@nvidia.com>,
	LKML <linux-kernel@vger.kernel.org>,
	"DRI Development" <dri-devel@lists.freedesktop.org>,
	"Christoph Hellwig" <hch@infradead.org>,
	"Linux MM" <linux-mm@kvack.org>,
	"Jérôme Glisse" <jglisse@redhat.com>,
	"Daniel Vetter" <daniel.vetter@intel.com>,
	"Dan Williams" <dan.j.williams@intel.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Linux ARM" <linux-arm-kernel@lists.infradead.org>,
	"open list:DMA BUFFER SHARING FRAMEWORK"
	<linux-media@vger.kernel.org>
Subject: Re: [PATCH v6 17/17] RFC: mm: add mmu_notifier argument to follow_pfn
Date: Wed, 25 Nov 2020 10:00:42 +0100
Message-ID: <CAKMK7uESguiML9eBonfU59T9fcfP4x18t=+nLdV8kMSc4mrs8A@mail.gmail.com> (raw)
In-Reply-To: <20201124155526.GH5487@ziepe.ca>

On Wed, Nov 25, 2020 at 9:13 AM Jason Gunthorpe <jgg@ziepe.ca> wrote:
>
> On Tue, Nov 24, 2020 at 03:28:14PM +0100, Daniel Vetter wrote:
> > 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.
>
> It looks like only some arches have selectable CONFIG_MMU: arm,
> m68k, microblaze, riscv, sh
>
> If we look at arches that work with HAVE_KVM, I only see: arm64, mips,
> powerpc, s390, x86
>
> So my conclusion is there is no intersection between !MMU and HAVE_KVM?
>
> > 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.
>
> This is what I was thinking might work

Makes sense, I'll do that for the next round.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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  reply index

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-19 14:41 [PATCH v6 00/17] follow_pfn and other iomap races Daniel Vetter
2020-11-19 14:41 ` [PATCH v6 01/17] drm/exynos: Stop using frame_vector helpers Daniel Vetter
2020-11-19 14:41 ` [PATCH v6 02/17] drm/exynos: Use FOLL_LONGTERM for g2d cmdlists Daniel Vetter
2020-11-19 14:41 ` [PATCH v6 03/17] misc/habana: Stop using frame_vector helpers Daniel Vetter
2020-11-21 12:47   ` Oded Gabbay
2020-11-19 14:41 ` [PATCH v6 04/17] misc/habana: Use FOLL_LONGTERM for userptr Daniel Vetter
2020-11-21 10:15   ` Oded Gabbay
2020-11-19 14:41 ` [PATCH v6 05/17] mm/frame-vector: Use FOLL_LONGTERM Daniel Vetter
2020-11-19 14:41 ` [PATCH v6 06/17] media: videobuf2: Move frame_vector into media subsystem Daniel Vetter
2020-11-20  8:07   ` Hans Verkuil
2020-11-19 14:41 ` [PATCH v6 07/17] mm: Close race in generic_access_phys Daniel Vetter
2020-11-19 14:41 ` [PATCH v6 08/17] mm: Add unsafe_follow_pfn Daniel Vetter
2020-11-19 14:41 ` [PATCH v6 09/17] media/videbuf1|2: Mark follow_pfn usage as unsafe Daniel Vetter
2020-11-20  8:06   ` Hans Verkuil
2020-11-20  8:28     ` Hans Verkuil
2020-11-20  8:32       ` Tomasz Figa
2020-11-20  9:18       ` Daniel Vetter
2020-11-20 10:38         ` Hans Verkuil
2020-11-20 10:51           ` Daniel Vetter
2020-11-20 12:08             ` Hans Verkuil
2020-11-20 12:23               ` Tomasz Figa
2020-11-24 14:16                 ` Daniel Vetter
2020-11-19 14:41 ` [PATCH v6 10/17] vfio/type1: Mark follow_pfn " Daniel Vetter
2020-11-19 14:41 ` [PATCH v6 11/17] PCI: Obey iomem restrictions for procfs mmap Daniel Vetter
2020-11-19 14:41 ` [PATCH v6 12/17] /dev/mem: Only set filp->f_mapping Daniel Vetter
2020-11-19 14:41 ` [PATCH v6 13/17] resource: Move devmem revoke code to resource framework Daniel Vetter
2020-11-19 14:41 ` [PATCH v6 14/17] sysfs: Support zapping of binary attr mmaps Daniel Vetter
2020-11-19 14:41 ` [PATCH v6 15/17] PCI: Revoke mappings like devmem Daniel Vetter
2020-11-19 14:41 ` [PATCH v6 16/17] RFC: kvm: pass kvm argument to follow_pfn callsites Daniel Vetter
2020-11-20 15:33   ` Paolo Bonzini
2020-11-20 15:44     ` Daniel Vetter
2020-11-20 15:55       ` Paolo Bonzini
2020-11-19 14:41 ` [PATCH v6 17/17] RFC: mm: add mmu_notifier argument to follow_pfn Daniel Vetter
2020-11-20 18:30   ` Jason Gunthorpe
2020-11-24 14:28     ` Daniel Vetter
2020-11-24 15:55       ` Jason Gunthorpe
2020-11-25  9:00         ` Daniel Vetter [this message]
2020-11-27 13:12 ` [PATCH v6 00/17] follow_pfn and other iomap races Jason Gunthorpe
2020-11-27 15:36   ` Daniel Vetter

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