Commit ca2f5466 authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

KVM: nVMX: Don't speculatively write virtual-APIC page address 



The VIRTUAL_APIC_PAGE_ADDR in vmcs02 is guaranteed to be updated before
it is consumed by hardware, either in nested_vmx_enter_non_root_mode()
or via the KVM_REQ_GET_VMCS12_PAGES callback.  Avoid an extra VMWRITE
and only stuff a bad value into vmcs02 when mapping vmcs12's address
fails.  This also eliminates the need for extra comments to connect the
dots between prepare_vmcs02_early() and nested_get_vmcs12_pages().

Signed-off-by: default avatarSean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 73cb8556

arch/x86/kvm/vmx/nested.c

+8 −13
Original line number Diff line number Diff line
@@ -2039,20 +2039,13 @@ static void prepare_vmcs02_early(struct vcpu_vmx *vmx, struct vmcs12 *vmcs12) 
	exec_control &= ~CPU_BASED_TPR_SHADOW;

	exec_control |= vmcs12->cpu_based_vm_exec_control;



	/*

	 * Write an illegal value to VIRTUAL_APIC_PAGE_ADDR. Later, if

	 * nested_get_vmcs12_pages can't fix it up, the illegal value

	 * will result in a VM entry failure.

	 */

	if (exec_control & CPU_BASED_TPR_SHADOW) {

		vmcs_write64(VIRTUAL_APIC_PAGE_ADDR, -1ull);

	if (exec_control & CPU_BASED_TPR_SHADOW)

		vmcs_write32(TPR_THRESHOLD, vmcs12->tpr_threshold);

	} else {

#ifdef CONFIG_X86_64

	else

		exec_control |= CPU_BASED_CR8_LOAD_EXITING |

				CPU_BASED_CR8_STORE_EXITING;

#endif

	}



	/*

	 * A vmexit (to either L1 hypervisor or L0 userspace) is always needed
@@ -2861,10 +2854,6 @@ static void nested_get_vmcs12_pages(struct kvm_vcpu *vcpu) 
	if (nested_cpu_has(vmcs12, CPU_BASED_TPR_SHADOW)) {

		map = &vmx->nested.virtual_apic_map;



		/*

		 * If translation failed, VM entry will fail because

		 * prepare_vmcs02 set VIRTUAL_APIC_PAGE_ADDR to -1ull.

		 */

		if (!kvm_vcpu_map(vcpu, gpa_to_gfn(vmcs12->virtual_apic_page_addr), map)) {

			vmcs_write64(VIRTUAL_APIC_PAGE_ADDR, pfn_to_hpa(map->pfn));

		} else if (nested_cpu_has(vmcs12, CPU_BASED_CR8_LOAD_EXITING) &&
@@ -2880,6 +2869,12 @@ static void nested_get_vmcs12_pages(struct kvm_vcpu *vcpu) 
			 */

			vmcs_clear_bits(CPU_BASED_VM_EXEC_CONTROL,

					CPU_BASED_TPR_SHADOW);

		} else {

			/*

			 * Write an illegal value to VIRTUAL_APIC_PAGE_ADDR to

			 * force VM-Entry to fail.

			 */

			vmcs_write64(VIRTUAL_APIC_PAGE_ADDR, -1ull);

		}

	}