From: Thomas Hellstrom <thellstrom@vmware.com>
To: "mhocko@kernel.org" <mhocko@kernel.org>,
"thomas_os@shipmail.org" <thomas_os@shipmail.org>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"kirill.shutemov@linux.intel.com"
<kirill.shutemov@linux.intel.com>,
"willy@infradead.org" <willy@infradead.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"christian.koenig@amd.com" <christian.koenig@amd.com>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
Pv-drivers <Pv-drivers@vmware.com>,
"rcampbell@nvidia.com" <rcampbell@nvidia.com>,
"dri-devel@lists.freedesktop.org"
<dri-devel@lists.freedesktop.org>,
"jglisse@redhat.com" <jglisse@redhat.com>,
Linux-graphics-maintainer <Linux-graphics-maintainer@vmware.com>
Subject: Re: [PATCH v3 2/2] mm, drm/ttm: Fix vm page protection handling
Date: Fri, 6 Dec 2019 14:16:10 +0000 [thread overview]
Message-ID: <10c4835486275e87334058bc2f406609c55271eb.camel@vmware.com> (raw)
In-Reply-To: <20191206103055.GO28317@dhcp22.suse.cz>
Hi Michal,
On Fri, 2019-12-06 at 11:30 +0100, Michal Hocko wrote:
> On Fri 06-12-19 09:24:26, Thomas Hellström (VMware) wrote:
> [...]
> > @@ -283,11 +282,26 @@ vm_fault_t ttm_bo_vm_fault_reserved(struct
> > vm_fault *vmf,
> > pfn = page_to_pfn(page);
> > }
> >
> > + /*
> > + * Note that the value of @prot at this point may
> > differ from
> > + * the value of @vma->vm_page_prot in the caching- and
> > + * encryption bits. This is because the exact location
> > of the
> > + * data may not be known at mmap() time and may also
> > change
> > + * at arbitrary times while the data is mmap'ed.
> > + * This is ok as long as @vma->vm_page_prot is not used
> > by
> > + * the core vm to set caching- and encryption bits.
> > + * This is ensured by core vm using pte_modify() to
> > modify
> > + * page table entry protection bits (that function
> > preserves
> > + * old caching- and encryption bits), and the @fault
> > + * callback being the only function that creates new
> > + * page table entries.
> > + */
>
> While this is a very valuable piece of information I believe we need
> to
> document this in the generic code where everybody will find it.
> vmf_insert_mixed_prot sounds like a good place to me. So being
> explicit
> about VM_MIXEDMAP. Also a reference from vm_page_prot to this
> function
> would be really helpeful.
>
> Thanks!
>
Just to make sure I understand correctly. You'd prefer this (or
similar) text to be present at the vmf_insert_mixed_prot() and
vmf_insert_pfn_prot() definitions for MIXEDMAP and PFNMAP respectively,
and a pointer from vm_page_prot to that text. Is that correct?
Thanks,
Thomas
next prev parent reply other threads:[~2019-12-06 14:16 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-06 8:24 [PATCH v3 0/2] mm, drm/ttm: Fix pte insertion with customized protection Thomas Hellström (VMware)
2019-12-06 8:24 ` [PATCH v3 1/2] mm: Add a vmf_insert_mixed_prot() function Thomas Hellström (VMware)
2019-12-06 8:24 ` [PATCH v3 2/2] mm, drm/ttm: Fix vm page protection handling Thomas Hellström (VMware)
2019-12-06 10:30 ` Michal Hocko
2019-12-06 14:16 ` Thomas Hellstrom [this message]
2019-12-06 14:24 ` Michal Hocko
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=10c4835486275e87334058bc2f406609c55271eb.camel@vmware.com \
--to=thellstrom@vmware.com \
--cc=Linux-graphics-maintainer@vmware.com \
--cc=Pv-drivers@vmware.com \
--cc=akpm@linux-foundation.org \
--cc=christian.koenig@amd.com \
--cc=dri-devel@lists.freedesktop.org \
--cc=jglisse@redhat.com \
--cc=kirill.shutemov@linux.intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mhocko@kernel.org \
--cc=rcampbell@nvidia.com \
--cc=thomas_os@shipmail.org \
--cc=willy@infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).