Re: [PATCH v3 7/9] KVM: nSVM: implement nested_svm_load_cr3() and use it for host->guest switch

Vitaly Kuznetsov
2020-07-10T11:40:46Z

Paolo Bonzini <pbonzini@redhat.com> writes:

> On 09/07/20 19:57, Paolo Bonzini wrote:
>> On 09/07/20 16:53, Vitaly Kuznetsov wrote:
>>> + if (nested_npt_enabled(svm))
>>> + nested_svm_init_mmu_context(&svm->vcpu);
>>> +
>>> ret = nested_svm_load_cr3(&svm->vcpu, nested_vmcb->save.cr3,
>>> nested_npt_enabled(svm));
>>
>> This needs to be done in svm_set_nested_state, so my suggestion is that
>> the previous patch includes a call to nested_svm_load_cr3 in
>> svm_set_nested_state, and this one adds the "if" inside
>> nested_svm_load_cr3 itself.
>
> Actually no, that doesn't work after the next patch. So the best option
> is probably to extract nested_svm_init_mmu as a separate step in
> enter_svm_guest_mode. This also leaves nested_prepare_vmcb_save as a
> void function.
>

Hm, it seems I missed svm_set_nested_state() path
completely. Surprisingly, state_test didn't fail)

I'm struggling a bit to understand why we don't have kvm_set_cr3() on
svm_set_nested_state() path: enter_svm_guest_mode() does it through
nested_prepare_vmcb_save() but it is skipped in svm_set_nested_state().
Don't we need it at least for !npt_enabled case? We'll have to extract
nested_cr3 from nested_vmcb then.

--
Vitaly