[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: [Xen-devel] [PATCH 0/5] VT-d support for PV guests
>From: Tian, Kevin >Sent: 2008年5月21日 13:56 > >>From: Ian Pratt [mailto:Ian.Pratt@xxxxxxxxxxxxx] >>Sent: 2008年5月21日 13:32 >> >>The IOMMU TLB doesn't cache not_present entries, hence you >>don't need to >>do a flush when transitioning an entry from not_present to >>present. Some >>IOMMUs will also re-walk the pagetable if they find a TLB >entry that is >>read-only and the operation is a write, but I can't recall whether VTd >>is like this. > >You're right, though VT-d spec defines a capability bit to indicate >whether VT-d may cache non-present entry or not. In reality it >doesn't make sense to do that. > >For promotion from non-present to present, then no flush is required. >But for promotion from read-only to read-write, I guess flush has to >be forced. Not sure whether currently such grant entry exists to >switch RO/RW permission on demand. Forgot above, I'm just talking exact same thing as you already pointed out. :-P Thanks, Kevin _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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