Re: [PATCHv5 00/14] xen: fix many long-standing grant mapping bugs

[Konrad Rzeszutek Wilk <konrad@darnok.org>]

On Tue, Jan 27, 2015 at 04:44:02PM +0000, David Vrabel wrote:
> This series fixes a number of long-standing bugs in the handling of
> grant maps.  Refer to the following for all the details.
> 
>   http://xenbits.xen.org/people/dvrabel/grant-improvements-C.pdf
> 
> In summary, the important uses that this enables are:
> 
> 1. Block backends can use networked storage safely.
> 
> 2. Block backends can use network storage provided by other guests on
>    the same host.
> 
> 3. User space block backends can use direct I/O or asynchronous I/O.
> 
> The first two patches are the core MM changes necessary.  These have
> already been acked.
> 
> Patches #3 and #4 remove existing (broken) mechanisms.  This does
> temporarily break some previously working use cases, but it does make
> the subsequent additions much easier to review.
> 
> Only patches #3, #4, and #13 need acks from other Xen maintainers.

I took a look at the patches and they look good to me.

> 
> As a happy side effect, performance is also likely to be improved in
> some areas (but I've not got any measurements yet).  User space
> backends using grant mapping should see some good improvements from
> reduced overheads and better unmap batching.  VIF to VIF network
> traffic may also see a small improvement.
> 
> Finally, thanks to Jenny who did much of the implementation.
> 
> Changes in v5:
> - Fix gntdev for auto-xlate guests.
> 
> Changes in v4:
> - Removed xen_blkbk_unmap_done().
> - Fixed bug in blkback when using mixed persistent and non-persistent
>   grants.
> 
> Changes in v3:
> - find_page renamed to find_special_page.
> - Added documentation for mm changes.
> - Fixed mangled forward port of blkback's safe unmap patch.
> - Export gnttab_alloc_pages() and gnttab_free_pages().
> - Fix 32-bit build.
> 
> Changes in v2:
> - Add find_page() VMA op instead of pages field (so struct
>   vm_area_struct doesn't increase in size.
> - Make foreign page tracking arch-independant and improve the API.
> - Alloc extra memory (for 32-bit archs) for the (domain, gref) when
>   allocating the page (instead of during the map).
> - Convert gntdev's lock to a mutex.
> 
> David
> 
> 
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