KVM: nVMX: stop abusing need_vmcs12_to_shadow_sync for eVMCS mapping (e942dbf8) · Commits · 戴 / test

When vmx_set_nested_state() happens, we may not have all the required data to map enlightened VMCS: e.g. HV_X64_MSR_VP_ASSIST_PAGE MSR may not yet be restored so we need a postponed action. Currently, we (ab)use need_vmcs12_to_shadow_sync/nested_sync_vmcs12_to_shadow() for that but this is not ideal: - We may not need to sync anything if L2 is running - It is hard to propagate errors from nested_sync_vmcs12_to_shadow() as we call it from vmx_prepare_switch_to_guest() which happens just before we do VMLAUNCH, the code is not ready to handle errors there. Move eVMCS mapping to nested_get_vmcs12_pages() and request KVM_REQ_GET_VMCS12_PAGES, it seems to be is less abusive in nature. It would probably be possible to introduce a specialized KVM_REQ_EVMCS_MAP but it is undesirable to propagate eVMCS specifics all the way up to x86.c Note, we don't need to request KVM_REQ_GET_VMCS12_PAGES from vmx_set_nested_state() directly as nested_vmx_enter_non_root_mode() already does that. Requesting KVM_REQ_GET_VMCS12_PAGES is done to document the (non-obvious) side-effect and to be future proof. Signed-off-by:

Vitaly Kuznetsov <vkuznets@redhat.com> Signed-off-by:

Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx/nested.c

+13 −11

Original line number	Diff line number	Diff line
		@@ -1996,14 +1996,6 @@ void nested_sync_vmcs12_to_shadow(struct kvm_vcpu *vcpu)
		{
		struct vcpu_vmx *vmx = to_vmx(vcpu);

		/*
		* hv_evmcs may end up being not mapped after migration (when
		* L2 was running), map it here to make sure vmcs12 changes are
		* properly reflected.
		*/
		if (vmx->nested.enlightened_vmcs_enabled && !vmx->nested.hv_evmcs)
		nested_vmx_handle_enlightened_vmptrld(vcpu, false);

		if (vmx->nested.hv_evmcs) {
		copy_vmcs12_to_enlightened(vmx);
		/* All fields are clean */
		@@ -3062,6 +3054,14 @@ static bool nested_get_vmcs12_pages(struct kvm_vcpu *vcpu)
		struct page *page;
		u64 hpa;

		/*
		* hv_evmcs may end up being not mapped after migration (when
		* L2 was running), map it here to make sure vmcs12 changes are
		* properly reflected.
		*/
		if (vmx->nested.enlightened_vmcs_enabled && !vmx->nested.hv_evmcs)
		nested_vmx_handle_enlightened_vmptrld(vcpu, false);

		if (nested_cpu_has2(vmcs12, SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES)) {
		/*
		* Translate L1 physical address to host physical
		@@ -5904,10 +5904,12 @@ static int vmx_set_nested_state(struct kvm_vcpu *vcpu,
		set_current_vmptr(vmx, kvm_state->hdr.vmx.vmcs12_pa);
		} else if (kvm_state->flags & KVM_STATE_NESTED_EVMCS) {
		/*
		* Sync eVMCS upon entry as we may not have
		* HV_X64_MSR_VP_ASSIST_PAGE set up yet.
		* nested_vmx_handle_enlightened_vmptrld() cannot be called
		* directly from here as HV_X64_MSR_VP_ASSIST_PAGE may not be
		* restored yet. EVMCS will be mapped from
		* nested_get_vmcs12_pages().
		*/
		vmx->nested.need_vmcs12_to_shadow_sync = true;
		kvm_make_request(KVM_REQ_GET_VMCS12_PAGES, vcpu);
		} else {
		return -EINVAL;
		}

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