Entering SMM while running in guest mode wasn't working very well because several
pieces of the vcpu state were left set up for nested operation.
Some of the issues observed:
* L1 was getting unexpected VM exits (using L1 interception controls but running
in SMM execution environment)
* SMM handler couldn't write to vmx_set_cr4 because of incorrect validity checks
predicated on nested.vmxon
* MMU was confused (walk_mmu was still set to nested_mmu)
Intel SDM actually prescribes the logical processor to "leave VMX operation" upon
entering SMM in 34.14.1 Default Treatment of SMI Delivery. What we need to do is
basically get out of guest mode and set nested.vmxon to false for the duration of
SMM. All this completely transparent to L1, i.e. L1 is not given control and no
L1 observable state changes.
To avoid code duplication this commit takes advantage of the existing nested
vmexit and run functionality, perhaps at the cost of efficiency. To get out of
guest mode, nested_vmx_vmexit with exit_reason == -1 is called, a trick already
used in vmx_leave_nested. Re-entering is cleaner, using enter_vmx_non_root_mode.
This commit fixes running Windows Server 2016 with Hyper-V enabled in a VM with
OVMF firmware (OVMF_CODE-need-smm.fd).
Signed-off-by: Ladi Prosek <lprosek@xxxxxxxxxx>
---
arch/x86/kvm/vmx.c | 58 +++++++++++++++++++++++++++++++++++++++++++-----------
1 file changed, 47 insertions(+), 11 deletions(-)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 8b2687ec8623..f37514f1d9cb 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -481,6 +481,14 @@ struct nested_vmx {
u64 nested_vmx_cr4_fixed0;
u64 nested_vmx_cr4_fixed1;
u64 nested_vmx_vmcs_enum;
+
+ /* SMM related state */
+ struct {
+ /* in VMX operation on SMM entry? */
+ bool vmxon;
+ /* in guest mode on SMM entry? */
+ bool guest_mode;
+ } smm;
};
#define POSTED_INTR_ON 0
@@ -11112,8 +11120,11 @@ static void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 exit_reason,
WARN_ON_ONCE(vmx->nested.nested_run_pending);
leave_guest_mode(vcpu);
- prepare_vmcs12(vcpu, vmcs12, exit_reason, exit_intr_info,
- exit_qualification);
+ if (exit_reason == -1)
+ sync_vmcs12(vcpu, vmcs12);
+ else
+ prepare_vmcs12(vcpu, vmcs12, exit_reason, exit_intr_info,
+ exit_qualification);
if (nested_vmx_store_msr(vcpu, vmcs12->vm_exit_msr_store_addr,
vmcs12->vm_exit_msr_store_count))
@@ -11139,12 +11150,13 @@ static void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 exit_reason,
INTR_INFO_VALID_MASK | INTR_TYPE_EXT_INTR;
}
- trace_kvm_nested_vmexit_inject(vmcs12->vm_exit_reason,
- vmcs12->exit_qualification,
- vmcs12->idt_vectoring_info_field,
- vmcs12->vm_exit_intr_info,
- vmcs12->vm_exit_intr_error_code,
- KVM_ISA_VMX);
+ if (exit_reason != -1)
+ trace_kvm_nested_vmexit_inject(vmcs12->vm_exit_reason,
+ vmcs12->exit_qualification,
+ vmcs12->idt_vectoring_info_field,
+ vmcs12->vm_exit_intr_info,
+ vmcs12->vm_exit_intr_error_code,
+ KVM_ISA_VMX);
vm_entry_controls_reset_shadow(vmx);
vm_exit_controls_reset_shadow(vmx);
@@ -11214,7 +11226,7 @@ static void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 exit_reason,
nested_vmx_failValid(vcpu, vm_inst_error);
} else
nested_vmx_succeed(vcpu);
- if (enable_shadow_vmcs)
+ if (enable_shadow_vmcs && exit_reason != -1)
vmx->nested.sync_shadow_vmcs = true;
/* in case we halted in L2 */
@@ -11631,18 +11643,42 @@ static void vmx_setup_mce(struct kvm_vcpu *vcpu)
static int vmx_smi_allowed(struct kvm_vcpu *vcpu)
{
+ /* we need a nested vmexit to enter SMM, postpone if run is pending */
+ if (to_vmx(vcpu)->nested.nested_run_pending)
+ return 0;
return 1;
}
static int vmx_prep_enter_smm(struct kvm_vcpu *vcpu, char *smstate)
{
- /* TODO: Implement */
+ struct vcpu_vmx *vmx = to_vmx(vcpu);
+
+ vmx->nested.smm.guest_mode = is_guest_mode(vcpu);
+ if (vmx->nested.smm.guest_mode)
+ nested_vmx_vmexit(vcpu, -1, 0, 0);
+
+ vmx->nested.smm.vmxon = vmx->nested.vmxon;
+ vmx->nested.vmxon = false;
return 0;
}
static int vmx_post_leave_smm(struct kvm_vcpu *vcpu)
{
- /* TODO: Implement */
+ struct vcpu_vmx *vmx = to_vmx(vcpu);
+ int ret;
+
+ if (vmx->nested.smm.vmxon) {
+ vmx->nested.vmxon = true;
+ vmx->nested.smm.vmxon = false;
+ }
+
+ if (vmx->nested.smm.guest_mode) {
+ ret = enter_vmx_non_root_mode(vcpu, false);
+ if (ret)
+ return ret;
+
+ vmx->nested.smm.guest_mode = false;
+ }
return 0;
}
--
2.13.5
