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@xxxxxxxxxx>
Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
---
arch/x86/kvm/vmx.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 702d4f51fa53..5a2566ee4975 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -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;
@@ -11907,13 +11915,14 @@ 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())
--
2.18.0
