On Thu, Aug 24, 2017 at 12:54:48PM +1000, Paul Mackerras wrote: > On Mon, Aug 21, 2017 at 05:00:36PM -0300, Thiago Jung Bauermann wrote: > > LoPAPR says: > > > > “ibm,processor-storage-keys” > > > > property name indicating the number of virtual storage keys supported > > by the processor described by this node. > > > > prop-encoded-array: Consists of two cells encoded as with encode-int. > > The first cell represents the number of virtual storage keys supported > > for data accesses while the second cell represents the number of > > virtual storage keys supported for instruction accesses. The cell value > > of zero indicates that no storage keys are supported for the access > > type. > > > > pHyp provides the property above but there's a bug in P8 firmware where the > > second cell is zero even though POWER8 supports instruction access keys. > > This bug will be fixed for P9. > > > > Tested with KVM on POWER8 Firenze machine and with TCG on x86_64 machine. > > > > Signed-off-by: Thiago Jung Bauermann <bauer...@linux.vnet.ibm.com> > > --- > > > > The sysfs files are provided by this patch for Linux: > > Those sysfs files relate to the kernel's support for userspace > processes using storage keys. That is quite distinct from KVM's > support for guests using storage keys, so I think that using those > sysfs files to indicate what the guest can do is wrong. > > In fact KVM allows guests to specify storage keys in the HPTE values > that they set, except that there is a bug (for which Ram Pai has > posted a patch) that means that KVM loses the top two bits of the key > number. > > What I would suggest is that we use the 'pad' field in the struct > kvm_ppc_smmu_info to report the number of keys supported by KVM for > guest use. That will be 0 in all current kernels, indicating that > keys are not supported, which is reasonable because of the bug. I > will make sure the patch fixing the bug goes in first.
with the current kernels, even with the bug, KVM can still support 8 keys. Should we say 8 instead of 0? It will help enable keys on KVM earlier and give a jump start to its adaption by applications. RP
