On Fri, Mar 2, 2018 at 10:55 AM, Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> wrote: > vmx_save_host_state() is only called from kvm_arch_vcpu_ioctl_run() so > the context is pretty well defined > True. > and MSR_FS_BASE should always be > equal to current->thread.fsbase. Not true. current->thread.fsbase is almost entirely undefined in this context. What you *could* do is export save_fsgs() and call it first. When FSGSBASE support lands (which will happen eventually!), the code in your patch will be completely wrong. Admittedly, your patch isn't 100% bogus, but the reason is subtle and you need lots of comments there *and* in save_fsgs().
