Re: Calling to kvm_mmu_load

[Paolo Bonzini <pbonzini@redhat.com>]

Il 21/10/2013 08:56, Arthur Chunqi Li ha scritto:
> Hi there,
> 
> I noticed that kvm_mmu_reload() is called every time in vcpu enter,
> and kvm_mmu_load() is called in this function when root_hpa is
> INVALID_PAGE. I get confused why and when root_hpa can be set to
> INVALID_PAGE? I find one condition that if vcpu get request
> KVM_REQ_MMU_RELOAD, kvm_mmu_unload() is called to invalid root_hpa,
> but this condition cannot cover all occasions.

Look also at mmu_free_roots, kvm_mmu_unload and kvm_mmu_reset_context.
In "normal" cases and without EPT, it should be called when CR3 changes
or when the paging mode changes (32-bit, PAE, 64-bit, no paging).  With
EPT, this kind of change won't reset the MMU (CR3 changes won't cause a
vmexit at all, in fact).

With nested virtualization, roots are invalidated whenever kvm->arch.mmu
changes meaning from L1->L0 or L2->L0 or vice versa (in the special case
where EPT is disabled on L0, this is trivially because vmentry loads CR3
from the vmcs02).

Paolo