On 09.05.2011, at 10:43, Avi Kivity wrote: > On 05/06/2011 01:25 PM, Carsten Otte wrote: >> From: Carsten Otte<cotte@xxxxxxxxxx> >> >> This patch gives userspace access to the guest visible storage keys. Three >> operations are supported: >> KVM_S390_KEYOP_SSKE for setting storage keys, similar to the set storage key >> extended (SSKE) instruction. >> KVM_S390_KEYOP_ISKE for reading storage key content, similar to the insert >> storage key extended (ISKE) instruction. >> KVM_s390_KEYOP_RRBE for reading and resetting the page reference bit, similar >> to the reset reference bit extended (RRBE) instruction. >> Note that all functions take userspace addresses as input, which typically >> differ from guest addresses. >> >> This work was requested by Alex Graf for guest live migration: Different from >> x86 the guest's view of dirty and reference information is not stored in the >> page table entrys that are part of the guest address space but are stored in >> the storage key instead. Thus, the storage key needs to be read, transfered, >> and written back on the migration target side. >> > > And not in main memory, either? Nope - storage keys are only accessible using special instructions. They're not in RAM (visible to a guest) :). 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
