[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 2/3] xen-fbfront: Use grant references when requested
On Fri, 2011-01-07 at 21:02 +0000, Daniel De Graaf wrote: > On 01/07/2011 03:44 PM, Ian Campbell wrote: > > More importantly there is also no way for the backend to figure out is > > the frontend is going to obey the request if it does write it (at least > > until it tries to map a gref and fails because its really got an mfn). > > The key used in xenstore (page-gref versus page-ref) tells the backend if > the request was honored. Oh yes, of course. I even suggested the same thing myself later on... > > Usually both front and backend would write a feature-foo node to their > > respective directory in xenstore and then figure out what to do based on > > what the other end wrote. > > Perhaps "use-grants" should be renamed to "feature-grants"? I think it would be more consistent with the other protocols (and the existing feature-update in the fb protocol) to do so. Also use-grants sounds a bit like a command rather than a suggestion to me. > I thought the > frontend writing a feature-grants node would be redundant since the > page-gref node already communicated what was chosen. Agreed. > > In the kbdfront patch you simply write both the mfn and the grant > > reference to xenstore, presumably the backend then just picks for itself > > which access method to use, could that approach be applicable here? > > Possible, but it would waste a bit of memory (a few extra pages for the > MFN tables in addition to the grant-ref tables). If this isn't an issue, > then fbfront can expose both and allow the backend to choose without any > negotiation. Is this preferred? Since you've already got the negotiation aspect covered I don't think there is any need go down this path. Ian. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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