[PATCH v3 15/15] KVM: nVMX: Don't load+put the vCPU when freeing nested state for a dying vCPU

[Sean Christopherson <seanjc@google.com>]

Drop the vcpu_{load,put}() pair when freeing nested state for a dying vCPU,
as nothing in what was free_nested() requires the vCPU to be loaded, common
x86 doesn't require the vCPU to be loaded when it's dying (because SVM
never loads the vCPU), KVM now explicitly handles taking the vCPU off the
PI wakeup list (was subtly being handled by vt_vcpu_pi_load()), and the
rest of vmx_vcpu_load() has no effects outside of loading/modifying the
VMCS or vCPU-specific metadata.

As for put(), because the vCPU obviously can't be loaded at the start of
nested_vmx_free_vcpu(), "guest_state_loaded" can't be true and thus
vmx_prepare_switch_to_host() must be a nop.  Similarly, the vCPU can't be
blocking when it's dying, and so vt_vcpu_pi_put() is also a nop (and if
it's not, that would be a fatal bug as it means the vCPU would be left on
the PI wakeup list after being freed).

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/vmx/nested.c | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 4a8f57eb3277..51183520f64a 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -330,7 +330,7 @@ static void nested_put_vmcs12_pages(struct kvm_vcpu *vcpu)
 	vmx->nested.pi_desc = NULL;
 }
 
-static void free_nested(struct kvm_vcpu *vcpu)
+void nested_vmx_free_vcpu(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 
@@ -390,14 +390,7 @@ static void nested_vmx_do_vmxoff(struct kvm_vcpu *vcpu)
 		free_vmcs(shadow_vmcs);
 	}
 
-	free_nested(vcpu);
-}
-
-void nested_vmx_free_vcpu(struct kvm_vcpu *vcpu)
-{
-	vcpu_load(vcpu);
-	free_nested(vcpu);
-	vcpu_put(vcpu);
+	nested_vmx_free_vcpu(vcpu);
 }
 
 #define EPTP_PA_MASK   GENMASK_ULL(51, 12)
-- 
2.56.0.307.g5fe7bd680c-goog