As long as we do not expose all the VMX related states to user space,
there is no way to properly reset a VCPU when VMX is enabled. Emulate
this for now by catching host-side clearings of the feature control MSR.
This allows to reboot a VM while it is running some hypervisor code.
Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
---
Better ideas? Or continue to leave it as it is?
arch/x86/kvm/vmx.c | 35 +++++++++++++++++++++++++++++++++++
1 file changed, 35 insertions(+)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index f90320b..da04247 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2455,6 +2455,8 @@ static int vmx_get_vmx_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 *pdata)
return 1;
}
+static void vmx_reset_nested(struct kvm_vcpu *vcpu);
+
static int vmx_set_vmx_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
{
u32 msr_index = msr_info->index;
@@ -2470,6 +2472,12 @@ static int vmx_set_vmx_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
& FEATURE_CONTROL_LOCKED)
return 0;
to_vmx(vcpu)->nested.msr_ia32_feature_control = data;
+ /*
+ * Detect reset and allow to leave VMX mode this way until we
+ * expose all related states to user space.
+ */
+ if (host_initialized && data == 0)
+ vmx_reset_nested(vcpu);
return 1;
}
@@ -8487,6 +8495,33 @@ static void nested_vmx_vmexit(struct kvm_vcpu *vcpu)
vmx->nested.sync_shadow_vmcs = true;
}
+static void vmx_reset_nested(struct kvm_vcpu *vcpu)
+{
+ struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
+ struct vcpu_vmx *vmx = to_vmx(vcpu);
+
+ if (!vmx->nested.vmxon)
+ return;
+
+ if (is_guest_mode(vcpu)) {
+ vmcs12->host_cr0 = X86_CR0_NW | X86_CR0_CD | X86_CR0_ET;
+ vmcs12->host_cr3 = 0;
+ vmcs12->host_cr4 = 0;
+ vmcs12->host_rsp = 0;
+ vmcs12->vm_exit_controls = 0;
+ nested_vmx_vmexit(vcpu);
+ }
+
+ free_nested(vmx);
+
+ /*
+ * If we were in guest mode, the reset state user space wrote so far
+ * is now inconsistent. If we were in host mode, some state update may
+ * have been rejected. So simply repeat the reset her.
+ */
+ vmx_vcpu_reset(vcpu);
+}
+
/*
* L1's failure to enter L2 is a subset of a normal exit, as explained in
* 23.7 "VM-entry failures during or after loading guest state" (this also
--
1.8.1.1.298.ge7eed54
--
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