On Tue, Jan 29, 2019 at 04:19:34PM +0100, Paolo Bonzini wrote: > On 28/01/19 11:33, Yang Weijiang wrote: > >> There is no code in this series to pass these fields to and from > >> userspace, and also to save/restore U_CET, INT_SSP_TAB, PL0_SSP and > >> PL3_SSP across context switches. > >> > > The kernel consumes these MSRs, please see kernel CET patch: > > https://lkml.org/lkml/fancy/2018/11/20/225 > > Still, even if the kernel saves these fields across context switch in > XSAVE areas, KVM must support accesses to the MSRs from userspace, for > example in order to perform live migration. > > For example, when reading/writing these in kvm_set_msr or > kvm_get_msr_common, you would have to do a read/write from the host > MSRs. You also have to put kvm_load_guest_fpu/kvm_put_guest_fpu calls > in __msr_io. Paolo, can you elaborate on why KVM would read the host MSRs? Wouldn't kvm_{get,set}_msr() pull the values from the VMCS when necessary?
