On Fri, Apr 17, 2020 at 12:03:18PM +0200, Vitaly Kuznetsov wrote: > Dexuan Cui <decui@xxxxxxxxxxxxx> writes: > > > Unlike the other CPUs, CPU0 is never offlined during hibernation. So in the > > resume path, the "new" kernel's VP assist page is not suspended (i.e. > > disabled), and later when we jump to the "old" kernel, the page is not > > properly re-enabled for CPU0 with the allocated page from the old kernel. > > > > So far, the VP assist page is only used by hv_apic_eoi_write(). > > No, not only for that ('git grep hv_get_vp_assist_page') > > KVM on Hyper-V also needs VP assist page to use Enlightened VMCS. In > particular, Enlightened VMPTR is written there. > > This makes me wonder: how does hibernation work with KVM in case we use > Enlightened VMCS and we have VMs running? We need to make sure VP Assist > page content is preserved. The page itself is preserved, isn't it? hv_cpu_die never frees the vp_assit page. It merely disables it. hv_cpu_init only allocates a new page if necessary. Wei. > > -- > Vitaly >