Re: [PATCH 3/3] KVM: nVMX: Emulate EPTP switching for the L1 hypervisor

From	Bandan Das <bsd@redhat.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH 3/3] KVM: nVMX: Emulate EPTP switching for the L1 hypervisor
Date	2017-08-03 22:00 +0200
Message-ID	<uaurM-4Ef-19@gated-at.bofh.it> (permalink)
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Paolo Bonzini <pbonzini@redhat.com> writes:

> On 03/08/2017 13:39, David Hildenbrand wrote:
>>> +	/* AD, if set, should be supported */
>>> +	if ((address & VMX_EPT_AD_ENABLE_BIT)) {
>>> +		if (!enable_ept_ad_bits)
>>> +			return false;
>> In theory (I guess) we would have to check here if
>> (vmx->nested.nested_vmx_ept_caps & VMX_EPT_AD_BIT)
>
> Yes, that's a more correct check than enable_ept_ad_bits.
>
>>>
>>> +	page = nested_get_page(vcpu, vmcs12->eptp_list_address);
>>> +	if (!page)
>>> +		return 1;
>>> +
>>> +	l1_eptp_list = kmap(page);
>>> +	address = l1_eptp_list[index];
>>> +	accessed_dirty = !!(address & VMX_EPT_AD_ENABLE_BIT);
>> 
>> Minor nit: Can't you directly do
>> 
>> kunmap(page);
>> nested_release_page_clean(page);
>> 
>> at this point?
>> 
>> We can fix this up later.
>
> You actually can do simply kvm_vcpu_read_guest_page(vcpu,
> vmcs12->eptp_list_address >> PAGE_SHIFT, &address, index * 8, 8).

Thanks Paolo, for the interesting tip. David, I sent a new version with the correct
check for AD and using this instead of kmap(page).

> Paolo

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[PATCH 3/3] KVM: nVMX: Emulate EPTP switching for the L1 hypervisor Bandan Das <bsd@redhat.com> - 2017-08-02 01:30 +0200
  Re: [PATCH 3/3] KVM: nVMX: Emulate EPTP switching for the L1  hypervisor David Hildenbrand <david@redhat.com> - 2017-08-03 13:40 +0200
    Re: [PATCH 3/3] KVM: nVMX: Emulate EPTP switching for the L1  hypervisor David Hildenbrand <david@redhat.com> - 2017-08-03 14:50 +0200
    Re: [PATCH 3/3] KVM: nVMX: Emulate EPTP switching for the L1  hypervisor Paolo Bonzini <pbonzini@redhat.com> - 2017-08-03 14:50 +0200
      Re: [PATCH 3/3] KVM: nVMX: Emulate EPTP switching for the L1 hypervisor Bandan Das <bsd@redhat.com> - 2017-08-03 22:00 +0200

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