2016-07-01 10:42+0200, Paolo Bonzini: > On 01/07/2016 00:15, Andrew Honig wrote: >>> > + /* kvm_apic_map_get_logical_dest() expects multiples of 16 */ >>> > + size = round_up(max_id + 1, 16); >> Now that you're using the full range of apic_id values, could this >> calculation overflow? Perhaps max_id could be u64? > > Good point, but I wonder if it's a good idea to let userspace allocate > 32 GB of memory. :) Yes, both could happen. I'll change it to u64 to make it future proof. > Let's put a limit on the maximum supported APIC ID, and report it > through KVM_CHECK_EXTENSION on the new KVM_CAP_X2APIC_API capability. > If 767 is enough for Knights Landing, the allocation below fits in two > pages. If you need to make it higher, please change the allocation to > use kvm_kvzalloc and kvfree. We sort of have a capability for maximum APIC ID, KVM_MAX_VCPU_ID, because VCPU ID is initial APIC ID and x2APIC ID should always be the initial APIC ID. Userspace is able to change x2APIC with LAPIC_GET/SET ioctl -- what about forbidding that? > Last but not least... > > >> > + new = kzalloc(sizeof(struct kvm_apic_map) + > >> > + sizeof(struct kvm_lapic) * size, GFP_KERNEL); > ^^^^^^^^^^^^^^^^^^^^^^^^ > ... the sizeof here must be sizeof(struct kvm_lapic *). Oops, thanks. -- 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
