RE: [Xen-devel] GNTTABOP_unmap_grant_ref

["King, Steven R" <steven.r.king@xxxxxxxxx>]

Vma->close() didn't work.  Thanks for the great suggestion though.  :^)

To verify that I wasn't making some new mistake, inspection of
linux/mm/mmap.c shows that Linux calls vma->close() *after* the page
table manipulation.  In do_munmap(), the sequence is:

detach_vmas_to_be_unmapped()
unmap_region()       <--- page table manipulation buried in here
remove_vma_list()    <--- vma->close() buried in here

Is this turning into a Xen problem?  Why does Xen forbid implicit
unmapping of shared pages?

-steve


-----Original Message-----
From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
[mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Muli
Ben-Yehuda
Sent: Tuesday, January 24, 2006 3:50 PM
To: King, Steven R
Cc: xen-devel; Mark Williamson
Subject: Re: [Xen-devel] GNTTABOP_unmap_grant_ref

On Tue, Jan 24, 2006 at 03:28:55PM -0800, King, Steven R wrote:

> I have not yet found a way to make the GNTTABOP_unmap_grant_ref() call

> in time to avoid the crash.  The driver release() function is too late

> and there's no hook in struct file_operations to handle unmap 
> explicitly.

Could you hook the vma->close function? ISTR it gets called on unmap. If
this is too fine grained or is not called on every munmap (unmapping of
partial VMAs?), you could clean up all mappings when the file that the
application mmap's is closed.

Cheers,
Muli
--
Muli Ben-Yehuda
http://www.mulix.org | http://mulix.livejournal.com/


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