On Tue, 2011-01-25 at 17:35 +0100, Jan Kiszka wrote: > On 2011-01-25 15:53, Avi Kivity wrote: > > On 01/25/2011 04:41 PM, Alex Williamson wrote: > >> > > > >> > > > >> > > kvm: Allow memory slot array to grow on demand > >> > > > >> > > Remove fixed KVM_MEMORY_SLOTS limit, allowing the slot array > >> > > to grow on demand. Private slots are now allocated at the > >> > > front instead of the end. Only x86 seems to use private slots, > >> > > >> > Hmm, doesn't current user space expect slots 8..11 to be the private > >> > ones and wouldn't it cause troubles if slots 0..3 are suddenly > >> reserved? > >> > >> The private slots aren't currently visible to userspace, they're > >> actually slots 32..35. The patch automatically increments user passed > >> slot ids so userspace has it's own zero-based view of the array. > >> Frankly, I don't understand why userspace reserves slots 8..11, is this > >> compatibility with older kernel implementations? > > > > I think so. I believe these kernel versions are too old now to matter, > > but of course I can't be sure. > > Will check and enable those 4 additional slots for user space if we no > longer need to exclude them. Appears that the history goes something like this... * Once upon a time we had 8 memory slots * v2.6.24-4949-ge0d62c7 added 4 reserved slots above those 8 * v2.6.24-4950-gcbc9402 made use of slot 8 for tss * v2.6.24-4962-gf78e0e2 made use of slot 9 for tpr * v2.6.25-5341-gef2979b bumped the 8 slots to 32 * v2.6.26-rc1-13-gb7ebfb0 made use of slot 10 for ept * v2.6.28-4952-g6fe6397 moved the previously hard coded slots 8,9,10 up to KVM_MEMORY_SLOTS + {0,1,2} So we haven't needed to reserve 8..11 for a while and we've never made use of all 4 private slots. I should reduce that to 3 in my patch. Maybe there's a test we could do in userspace to figure out we don't have to skip those anymore? Alex -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html