[PATCH 3/3] KVM: nVMX: Rework event injection and recovery

Jan Kiszka
2013-03-13T16:53:54Z

The changes finally allow to inject interrupts directly from L0 to L2.

The basic idea is to always transfer the pending event injection on
vmexit into the architectural state of the VCPU and then drop it from
there if it turns out that we left L2 to enter L1.

VMX and SVM are now identical in how they recover event injections from
unperformed vmlaunch/vmresume: We detect that VM_ENTRY_INTR_INFO_FIELD
still contains a valid event and, if yes, transfer the content into L1's
idt_vectoring_info_field.

However, we differ on how to deal with events that L0 wanted to inject
into L2. Likely, this case is still broken in SVM. For VMX, the function
vmcs12_save_pending_events deals with transferring pending L0 events
into the queue of L1. That is mandatory as L1 may decide to switch the
guest state completely, invalidating or preserving the pending events
for later injection (including on a different node, once we support
migration).

Note that we treat directly injected NMIs differently as they can hit
both L1 and L2. In this case, we let L0 try to injection again also over
L1 after leaving L2.

To avoid that we incorrectly leak an event into the architectural VCPU
state that L1 wants to inject, we skip cancellation on nested run.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
arch/x86/kvm/vmx.c | 118 ++++++++++++++++++++++++++++++++++++++--------------
1 files changed, 87 insertions(+), 31 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 10de336..3ca5461 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -6559,8 +6559,6 @@ static void __vmx_complete_interrupts(struct kvm_vcpu *vcpu,

static void vmx_complete_interrupts(struct vcpu_vmx *vmx)
{
- if (is_guest_mode(&vmx->vcpu))
- return;
__vmx_complete_interrupts(&vmx->vcpu, vmx->idt_vectoring_info,
VM_EXIT_INSTRUCTION_LEN,
IDT_VECTORING_ERROR_CODE);
@@ -6568,7 +6566,7 @@ static void vmx_complete_interrupts(struct vcpu_vmx *vmx)

static void vmx_cancel_injection(struct kvm_vcpu *vcpu)
{
- if (is_guest_mode(vcpu))
+ if (to_vmx(vcpu)->nested.nested_run_pending)
return;
__vmx_complete_interrupts(vcpu,
vmcs_read32(VM_ENTRY_INTR_INFO_FIELD),
@@ -6601,21 +6599,6 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
struct vcpu_vmx *vmx = to_vmx(vcpu);
unsigned long debugctlmsr;

- if (is_guest_mode(vcpu) && !vmx->nested.nested_run_pending) {
- struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
- if (vmcs12->idt_vectoring_info_field &
- VECTORING_INFO_VALID_MASK) {
- vmcs_write32(VM_ENTRY_INTR_INFO_FIELD,
- vmcs12->idt_vectoring_info_field);
- vmcs_write32(VM_ENTRY_INSTRUCTION_LEN,
- vmcs12->vm_exit_instruction_len);
- if (vmcs12->idt_vectoring_info_field &
- VECTORING_INFO_DELIVER_CODE_MASK)
- vmcs_write32(VM_ENTRY_EXCEPTION_ERROR_CODE,
- vmcs12->idt_vectoring_error_code);
- }
- }
-
/* Record the guest's net vcpu time for enforced NMI injections. */
if (unlikely(!cpu_has_virtual_nmis() && vmx->soft_vnmi_blocked))
vmx->entry_time = ktime_get();
@@ -6774,17 +6757,6 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)

vmx->idt_vectoring_info = vmcs_read32(IDT_VECTORING_INFO_FIELD);

- if (is_guest_mode(vcpu)) {
- struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
- vmcs12->idt_vectoring_info_field = vmx->idt_vectoring_info;
- if (vmx->idt_vectoring_info & VECTORING_INFO_VALID_MASK) {
- vmcs12->idt_vectoring_error_code =
- vmcs_read32(IDT_VECTORING_ERROR_CODE);
- vmcs12->vm_exit_instruction_len =
- vmcs_read32(VM_EXIT_INSTRUCTION_LEN);
- }
- }
-
vmx->loaded_vmcs->launched = 1;

vmx->exit_reason = vmcs_read32(VM_EXIT_REASON);
@@ -7391,6 +7363,52 @@ vmcs12_guest_cr4(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
vcpu->arch.cr4_guest_owned_bits));
}

+static void vmcs12_save_pending_events(struct kvm_vcpu *vcpu,
+ struct vmcs12 *vmcs12)
+{
+ u32 idt_vectoring;
+ unsigned int nr;
+
+ /*
+ * We only transfer exceptions and maskable interrupts. It is fine if
+ * L0 retries to inject a pending NMI over L1.
+ */
+ if (vcpu->arch.exception.pending) {
+ nr = vcpu->arch.exception.nr;
+ idt_vectoring = nr | VECTORING_INFO_VALID_MASK;
+
+ if (kvm_exception_is_soft(nr)) {
+ vmcs12->vm_exit_instruction_len =
+ vcpu->arch.event_exit_inst_len;
+ idt_vectoring |= INTR_TYPE_SOFT_EXCEPTION;
+ } else
+ idt_vectoring |= INTR_TYPE_HARD_EXCEPTION;
+
+ if (vcpu->arch.exception.has_error_code) {
+ idt_vectoring |= VECTORING_INFO_DELIVER_CODE_MASK;
+ vmcs12->idt_vectoring_error_code =
+ vcpu->arch.exception.error_code;
+ }
+
+ vmcs12->idt_vectoring_info_field = idt_vectoring;
+ } else if (vcpu->arch.interrupt.pending) {
+ nr = vcpu->arch.interrupt.nr;
+ idt_vectoring = nr | VECTORING_INFO_VALID_MASK;
+
+ if (vcpu->arch.interrupt.soft) {
+ idt_vectoring |= INTR_TYPE_SOFT_INTR;
+ vmcs12->vm_entry_instruction_len =
+ vcpu->arch.event_exit_inst_len;
+ } else
+ idt_vectoring |= INTR_TYPE_EXT_INTR;
+
+ vmcs12->idt_vectoring_info_field = idt_vectoring;
+ }
+
+ kvm_clear_exception_queue(vcpu);
+ kvm_clear_interrupt_queue(vcpu);
+}
+
/*
* prepare_vmcs12 is part of what we need to do when the nested L2 guest exits
* and we want to prepare to run its L1 parent. L1 keeps a vmcs for L2 (vmcs12),
@@ -7482,9 +7500,47 @@ static void prepare_vmcs12(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
vmcs12->vm_exit_instruction_len = vmcs_read32(VM_EXIT_INSTRUCTION_LEN);
vmcs12->vmx_instruction_info = vmcs_read32(VMX_INSTRUCTION_INFO);

- /* clear vm-entry fields which are to be cleared on exit */
- if (!(vmcs12->vm_exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY))
+ if (!(vmcs12->vm_exit_reason & VMX_EXIT_REASONS_FAILED_VMENTRY)) {
+ if ((vmcs12->vm_entry_intr_info_field &
+ INTR_INFO_VALID_MASK) &&
+ (vmcs_read32(VM_ENTRY_INTR_INFO_FIELD) &
+ INTR_INFO_VALID_MASK)) {
+ /*
+ * Preserve the event that was supposed to be injected
+ * by L1 via emulating it would have been returned in
+ * IDT_VECTORING_INFO_FIELD.
+ */
+ vmcs12->idt_vectoring_info_field =
+ vmcs12->vm_entry_intr_info_field;
+ vmcs12->idt_vectoring_error_code =
+ vmcs12->vm_entry_exception_error_code;
+ vmcs12->vm_exit_instruction_len =
+ vmcs12->vm_entry_instruction_len;
+ vmcs_write32(VM_ENTRY_INTR_INFO_FIELD, 0);
+
+ /*
+ * We do not drop NMIs that targeted L2 below as they
+ * can also be reinjected over L1. But if this event
+ * was an NMI, it was synthetic and came from L1.
+ */
+ vcpu->arch.nmi_injected = false;
+ } else
+ /*
+ * Transfer the event L0 may wanted to inject into L2
+ * to IDT_VECTORING_INFO_FIELD.
+ */
+ vmcs12_save_pending_events(vcpu, vmcs12);
+
+ /* clear vm-entry fields which are to be cleared on exit */
vmcs12->vm_entry_intr_info_field &= ~INTR_INFO_VALID_MASK;
+ }
+
+ /*
+ * Drop what we picked up for L2 via vmx_complete_interrupts. It is
+ * preserved above and would only end up incorrectly in L1.
+ */
+ kvm_clear_exception_queue(vcpu);
+ kvm_clear_interrupt_queue(vcpu);
}

/*
--
1.7.3.4