Re: Nick's core remove PageReserved broke vmware...

[Michael S. Tsirkin]

Quoting Hugh Dickins <hugh@xxxxxxxxxxx>:
> Two warnings if someone would like to post a MADV_DONTCOPY patch.
> It should include a matching MADV_DOCOPY to clear the condition, but
> that must not be allowed to clear VM_DONTCOPY set originally by driver:
> perhaps you'll end up with a VM_UDONTCOPY or something like that.

Thanks!
All existing drivers that set VM_DONTCOPY also set VM_IO.
So lets just disable playing with these flags from madvise if VM_IO is set.
There's no reason I can see that the driver should have a say
on what the process does with its own (non-IO) memory.
Sounds good?

By the way, as a separate issue, we still have a problem with DMA to pages
which are *needed* by the child process. What do you think about VM_COPY
(to do the old unix thing of actually copying the page instead of
setting the COW flag) and a matching madvise call to set/clear it?

> And Badari has a MADV_REMOVE patch in the works, taking the next
> slot (just after MADV_DONTNEED in most of the arches): probably
> best for you to base yours on top of his (though yours is simpler
> and might jump ahead).
> 
> Hugh

Yep, I saw that posted for inclusion in -mm.

-- 
MST
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/