[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCHv1 0/2] xen/grant-table: fix PV guests and remove V2 support
On 04/07/14 13:01, Paul Durrant wrote: >> -----Original Message----- >> From: David Vrabel >> Sent: 04 July 2014 12:55 >> To: Paul Durrant; xen-devel@xxxxxxxxxxxxxxxxxxxx >> Cc: Boris Ostrovsky >> Subject: Re: [Xen-devel] [PATCHv1 0/2] xen/grant-table: fix PV guests and >> remove V2 support >> >> On 04/07/14 11:59, Paul Durrant wrote: >>>> -----Original Message----- >>>> From: xen-devel-bounces@xxxxxxxxxxxxx [mailto:xen-devel- >>>> bounces@xxxxxxxxxxxxx] On Behalf Of David Vrabel >>>> Sent: 02 July 2014 11:25 >>>> To: xen-devel@xxxxxxxxxxxxxxxxxxxx >>>> Cc: Boris Ostrovsky; David Vrabel >>>> Subject: [Xen-devel] [PATCHv1 0/2] xen/grant-table: fix PV guests and >>>> remove V2 support >>>> >>>> The first patch fixes a logn standing issue where the map/unmap of >>>> grant table frames by PV guests was unsafe and could BUG() or have >>>> other bad behaviour. This was caused by calling function that were >>>> not permitted from atomic contexts. >>>> >>>> The second patch removes all V2 table code since it is unused. >>>> >>> >>> How confident are you of that assertion? >> >> This is removing the /Linux/ code which has been using V1 only for a >> while now. >> > > If you believe that the API is likely to wither then that seems > reasonable. I would have thought the code was unlikely to see much > change though and it seems a shame to remove an interface to something > that it still there in Xen... I guess *someone* may want to use it in > future; particularly the copy-only grants could be useful for something > like IDC (if the backend was unprivileged). It's already withering. For example PVH doesn't support V2 as it doesn't handle mapping/populating the status frames. And fixing a long standing bug (see patch 1/2) was made more complicated by having to fix up the (unused) code for dealing with the status frames. And as an aside, I'm not convinced that copy-only grants are what's needed for IDC with untrusted backend. I think revocable grants are required for efficient usage of shared rings. David _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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