From: Peter Xu <peterx@redhat.com>
To: Jason Gunthorpe <jgg@ziepe.ca>
Cc: dan.j.williams@intel.com, Paolo Bonzini <pbonzini@redhat.com>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 0/2] KVM: do not assume PTE is writable after follow_pfn
Date: Mon, 8 Feb 2021 19:23:14 -0500 [thread overview]
Message-ID: <20210209002314.GC78818@xz-x1> (raw)
In-Reply-To: <20210208232625.GA4718@ziepe.ca>
On Mon, Feb 08, 2021 at 07:26:25PM -0400, Jason Gunthorpe wrote:
> On Mon, Feb 08, 2021 at 05:02:59PM -0500, Peter Xu wrote:
> > On Mon, Feb 08, 2021 at 02:51:33PM -0400, Jason Gunthorpe wrote:
> > > On Fri, Feb 05, 2021 at 01:14:11PM -0500, Peter Xu wrote:
> > >
> > > > But I do have a question on why dax as the only user needs to pass in the
> > > > notifier to follow_pte() for initialization.
> > >
> > > Not sure either, why does DAX opencode something very much like
> > > page_mkclean() with dax_entry_mkclean()?
> > >
> > > Also it looks like DAX uses the wrong notifier, it calls
> > > MMU_NOTIFY_CLEAR but page_mkclean_one() uses
> > > MMU_NOTIFY_PROTECTION_PAGE for the same PTE modification sequence??
> > >
> > > page_mkclean() has some technique to make the notifier have the right
> > > size without becoming entangled in the PTL locks..
> >
> > Right. I guess it's because dax doesn't have "struct page*" on the
> > back, so it
>
> It doesn't? I thought DAX cases did?
I'm not familiar with dax at all.. but it seems so: e.g. dax_iomap_pte_fault()
looks like the general fault handler for dax mappings, in which there's calls
to things like vmf_insert_mixed_mkwrite() trying to install ptes with raw pfn.
Or I could also be missing something very important.. Thanks,
--
Peter Xu
next prev parent reply other threads:[~2021-02-09 0:23 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-05 10:32 [PATCH 0/2] KVM: do not assume PTE is writable after follow_pfn Paolo Bonzini
2021-02-05 10:32 ` [PATCH 1/2] mm: provide a sane PTE walking API for modules Paolo Bonzini
2021-02-05 13:49 ` Jason Gunthorpe
2021-02-08 17:39 ` Christoph Hellwig
2021-02-08 18:18 ` Paolo Bonzini
2021-02-09 8:14 ` Christoph Hellwig
2021-02-09 9:19 ` Paolo Bonzini
2021-02-05 10:32 ` [PATCH 2/2] KVM: do not assume PTE is writable after follow_pfn Paolo Bonzini
2021-02-05 15:43 ` kernel test robot
2021-02-05 17:41 ` kernel test robot
2021-02-05 18:14 ` [PATCH 0/2] " Peter Xu
2021-02-08 18:51 ` Jason Gunthorpe
2021-02-08 22:02 ` Peter Xu
2021-02-08 23:26 ` Jason Gunthorpe
2021-02-09 0:23 ` Peter Xu [this message]
2021-02-09 8:19 ` Christoph Hellwig
2021-02-09 10:02 ` Joao Martins
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