KVM: nVMX: initialize vmcs02 constant exactly once (per VMCS) (9d6105b2) · Commits · 戴 / test

Add a dedicated flag to track if vmcs02 has been initialized, i.e. the constant state for vmcs02 has been written to the backing VMCS. The launched flag (in struct loaded_vmcs) gets cleared on logical CPU migration to mirror hardware behavior[1], i.e. using the launched flag to determine whether or not vmcs02 constant state needs to be initialized results in unnecessarily re-initializing the VMCS when migrating between logical CPUS. [1] The active VMCS needs to be VMCLEARed before it can be migrated to a different logical CPU. Hardware's VMCS cache is per-CPU and is not coherent between CPUs. VMCLEAR flushes the cache so that any dirty data is written back to memory. A side effect of VMCLEAR is that it also clears the VMCS's internal launch flag, which KVM must mirror because VMRESUME must be used to run a previously launched VMCS. Suggested-by:

Jim Mattson <jmattson@google.com> Signed-off-by:

Sean Christopherson <sean.j.christopherson@intel.com> Reviewed-by:

Jim Mattson <jmattson@google.com> Signed-off-by:

Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx.c

+11 −2

Original line number	Diff line number	Diff line
		@@ -833,6 +833,13 @@ struct nested_vmx {
		bool sync_shadow_vmcs;
		bool dirty_vmcs12;

		/*
		* vmcs02 has been initialized, i.e. state that is constant for
		* vmcs02 has been written to the backing VMCS. Initialization
		* is delayed until L1 actually attempts to run a nested VM.
		*/
		bool vmcs02_initialized;

		bool change_vmcs01_virtual_apic_mode;

		/* L2 must run next, and mustn't decide to exit to L1. */
		@@ -8278,6 +8285,7 @@ static int enter_vmx_operation(struct kvm_vcpu *vcpu)

		vmx->nested.vpid02 = allocate_vpid();

		vmx->nested.vmcs02_initialized = false;
		vmx->nested.vmxon = true;
		return 0;

		@@ -11982,13 +11990,14 @@ static u64 nested_vmx_calc_efer(struct vcpu_vmx vmx, struct vmcs12 vmcs12)
		static void prepare_vmcs02_constant_state(struct vcpu_vmx *vmx)
		{
		/*
		* If we have never launched vmcs02, set the constant vmcs02 state
		* If vmcs02 hasn't been initialized, set the constant vmcs02 state
		* according to L0's settings (vmcs12 is irrelevant here). Host
		* fields that come from L0 and are not constant, e.g. HOST_CR3,
		* will be set as needed prior to VMLAUNCH/VMRESUME.
		*/
		if (vmx->nested.vmcs02.launched)
		if (vmx->nested.vmcs02_initialized)
		return;
		vmx->nested.vmcs02_initialized = true;

		/* All VMFUNCs are currently emulated through L0 vmexits. */
		if (cpu_has_vmx_vmfunc())

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