Re: [PATCH] x86/hyperv: Suspend/resume the VP assist page for hibernation

Vitaly Kuznetsov
2020-04-17T10:03:27Z

Dexuan Cui <decui@microsoft.com> 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.

--
Vitaly