On 29/01/19 09:29, Yang Weijiang wrote: > 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? Live migration is generally a requirement for a feature to be accepted in KVM. Paolo >> 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. >>>
