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. Thanks, you're right, if we want to support live migration we need do that. However, this feature relies on quite a few external dependencies, e.g., cpu capabilities, kernel version and configuration, we don't support live migration right now. what's your opinion? > > Thanks, > > Paolo > > >> In addition, PL1_SSP and PL2_SSP should be supported even if the guest > >> doesn't use them. It makes sense to avoid intercepting them, but they > >> should still be supported and switched (possibly only if nonzero). > >> > >> Am I missing something, for example a dependency on host CET support? > >> If not, how was this series tested? > >> > > The guest CET feature is tested with kernel CET patches on internal > > virtual platform. > >
