On Sun, 2014-06-29 at 16:47 +0530, Aneesh Kumar K.V wrote: > To achieve the above we use virtual page calss protection mechanism for > covering (2) and (3). For both the above case we mark the hpte > valid, but associate the page with virtual page class index 30 and 31. > The authority mask register is configured such that class index 30 and 31 > will have read/write denied. The above change results in a key fault > for (2) and (3). This allows us to forward a NO_HPTE fault directly to guest > without doing the expensive hash pagetable lookup.
So we have a measurable performance benefit (about half a second out of 8) but you didn't explain the drawback here which is to essentially make it impossible for guests to exploit virtual page class keys, or did you find a way to still make that possible ? As it-is, it's not a huge issue for Linux but we might have to care with other OSes that do care... Do we have a way in PAPR to signify to the guest that the keys are not available ? Cheers, Ben. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
