On 11/20/2013 11:14 AM, David Herrmann wrote:
> Hi
>
> On Wed, Nov 20, 2013 at 10:55 AM, Thomas Hellstrom
> <thellstrom at vmware.com> wrote:
>> Not sure if there are any user-space users of private bo mappings, but
>> if there are, or will be, zapping the COW'd pages when, for example,
>> moving a bo would confuse the user immensely since the net effect for the
>> user would be that pages written to would lose their contents.
> You're only talking about moving bos, but what happens when you evict
> a bo? You *must* clear COW mappings, too. Otherwise, they might still
> get read-access to the evicted bo.
Hmm. When I talk about COW'd pages, I mean individual anonymous pages.
If there is a COW mapping left in a VMA, it points to an anonymous page
and will never access the evicted bo.
All (read-only-enabled) ptes pointing to the evicted bo would still be
zapped, so I'm afraid I don't understand your comment?
>
> Note that we currently cause SIGBUS on access to mmap'd bos if they
> are evicted and cannot be restored (think: user-space mapped the
> VESA-FB but a real driver took over). So maybe we want two independent
> helpers here?
It shouldn't be needed.
Thanks,
Thomas
>
> Thanks
> David
>
>> Signed-off-by: Thomas Hellstrom <thellstrom at vmware.com>
>> ---
>> include/drm/drm_vma_manager.h | 6 +++---
>> 1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/include/drm/drm_vma_manager.h b/include/drm/drm_vma_manager.h
>> index c18a593..347077d 100644
>> --- a/include/drm/drm_vma_manager.h
>> +++ b/include/drm/drm_vma_manager.h
>> @@ -231,9 +231,9 @@ static inline void drm_vma_node_unmap(struct
>> drm_vma_offset_node *node,
>> struct address_space *file_mapping)
>> {
>> if (file_mapping && drm_vma_node_has_offset(node))
>> - unmap_mapping_range(file_mapping,
>> - drm_vma_node_offset_addr(node),
>> - drm_vma_node_size(node) << PAGE_SHIFT,
>> 1);
>> + unmap_shared_mapping_range
>> + (file_mapping, drm_vma_node_offset_addr(node),
>> + drm_vma_node_size(node) << PAGE_SHIFT);
>> }
>>
>> /**
>> --
>> 1.7.10.4
