[PATCH v2 2/2] KVM: x86: emulate wait-for-SIPI and SIPI-VMExit
From: yadong . qi
Date: Fri Nov 06 2020 - 01:51:51 EST
From: Yadong Qi <yadong.qi@xxxxxxxxx>
Background: We have a lightweight HV, it needs INIT-VMExit and
SIPI-VMExit to wake-up APs for guests since it do not monitor
the Local APIC. But currently virtual wait-for-SIPI(WFS) state
is not supported in nVMX, so when running on top of KVM, the L1
HV cannot receive the INIT-VMExit and SIPI-VMExit which cause
the L2 guest cannot wake up the APs.
According to Intel SDM Chapter 25.2 Other Causes of VM Exits,
SIPIs cause VM exits when a logical processor is in
wait-for-SIPI state.
In this patch:
1. introduce SIPI exit reason,
2. introduce wait-for-SIPI state for nVMX,
3. advertise wait-for-SIPI support to guest.
When L1 hypervisor is not monitoring Local APIC, L0 need to emulate
INIT-VMExit and SIPI-VMExit to L1 to emulate INIT-SIPI-SIPI for
L2. L2 LAPIC write would be traped by L0 Hypervisor(KVM), L0 should
emulate the INIT/SIPI vmexit to L1 hypervisor to set proper state
for L2's vcpu state.
Handle procdure:
Source vCPU:
L2 write LAPIC.ICR(INIT).
L0 trap LAPIC.ICR write(INIT): inject a latched INIT event to target
vCPU.
Target vCPU:
L0 emulate an INIT VMExit to L1 if is guest mode.
L1 set guest VMCS, guest_activity_state=WAIT_SIPI, vmresume.
L0 set vcpu.mp_state to INIT_RECEIVED if (vmcs12.guest_activity_state
== WAIT_SIPI).
Source vCPU:
L2 write LAPIC.ICR(SIPI).
L0 trap LAPIC.ICR write(INIT): inject a latched SIPI event to traget
vCPU.
Target vCPU:
L0 emulate an SIPI VMExit to L1 if (vcpu.mp_state == INIT_RECEIVED).
L1 set CS:IP, guest_activity_state=ACTIVE, vmresume.
L0 resume to L2.
L2 start-up.
Signed-off-by: Yadong Qi <yadong.qi@xxxxxxxxx>
Message-Id: <20200922052343.84388-1-yadong.qi@xxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
v1->v2:
* sync_vmcs02_to_vmcs12(): set vmcs12->guest_activity_state to WAIT_SIPI
if vcpu's mp_state is INIT_RECEIVED state.
---
arch/x86/include/asm/vmx.h | 1 +
arch/x86/include/uapi/asm/vmx.h | 2 ++
arch/x86/kvm/vmx/nested.c | 55 ++++++++++++++++++++++++---------
3 files changed, 44 insertions(+), 14 deletions(-)
diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
index f8ba5289ecb0..38ca445a8429 100644
--- a/arch/x86/include/asm/vmx.h
+++ b/arch/x86/include/asm/vmx.h
@@ -113,6 +113,7 @@
#define VMX_MISC_PREEMPTION_TIMER_RATE_MASK 0x0000001f
#define VMX_MISC_SAVE_EFER_LMA 0x00000020
#define VMX_MISC_ACTIVITY_HLT 0x00000040
+#define VMX_MISC_ACTIVITY_WAIT_SIPI 0x00000100
#define VMX_MISC_ZERO_LEN_INS 0x40000000
#define VMX_MISC_MSR_LIST_MULTIPLIER 512
diff --git a/arch/x86/include/uapi/asm/vmx.h b/arch/x86/include/uapi/asm/vmx.h
index b8ff9e8ac0d5..ada955c5ebb6 100644
--- a/arch/x86/include/uapi/asm/vmx.h
+++ b/arch/x86/include/uapi/asm/vmx.h
@@ -32,6 +32,7 @@
#define EXIT_REASON_EXTERNAL_INTERRUPT 1
#define EXIT_REASON_TRIPLE_FAULT 2
#define EXIT_REASON_INIT_SIGNAL 3
+#define EXIT_REASON_SIPI_SIGNAL 4
#define EXIT_REASON_INTERRUPT_WINDOW 7
#define EXIT_REASON_NMI_WINDOW 8
@@ -94,6 +95,7 @@
{ EXIT_REASON_EXTERNAL_INTERRUPT, "EXTERNAL_INTERRUPT" }, \
{ EXIT_REASON_TRIPLE_FAULT, "TRIPLE_FAULT" }, \
{ EXIT_REASON_INIT_SIGNAL, "INIT_SIGNAL" }, \
+ { EXIT_REASON_SIPI_SIGNAL, "SIPI_SIGNAL" }, \
{ EXIT_REASON_INTERRUPT_WINDOW, "INTERRUPT_WINDOW" }, \
{ EXIT_REASON_NMI_WINDOW, "NMI_WINDOW" }, \
{ EXIT_REASON_TASK_SWITCH, "TASK_SWITCH" }, \
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 89af692deb7e..6dc9017289ba 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -2952,7 +2952,8 @@ static int nested_vmx_check_vmcs_link_ptr(struct kvm_vcpu *vcpu,
static int nested_check_guest_non_reg_state(struct vmcs12 *vmcs12)
{
if (CC(vmcs12->guest_activity_state != GUEST_ACTIVITY_ACTIVE &&
- vmcs12->guest_activity_state != GUEST_ACTIVITY_HLT))
+ vmcs12->guest_activity_state != GUEST_ACTIVITY_HLT &&
+ vmcs12->guest_activity_state != GUEST_ACTIVITY_WAIT_SIPI))
return -EINVAL;
return 0;
@@ -3559,19 +3560,29 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
*/
nested_cache_shadow_vmcs12(vcpu, vmcs12);
- /*
- * If we're entering a halted L2 vcpu and the L2 vcpu won't be
- * awakened by event injection or by an NMI-window VM-exit or
- * by an interrupt-window VM-exit, halt the vcpu.
- */
- if ((vmcs12->guest_activity_state == GUEST_ACTIVITY_HLT) &&
- !(vmcs12->vm_entry_intr_info_field & INTR_INFO_VALID_MASK) &&
- !(vmcs12->cpu_based_vm_exec_control & CPU_BASED_NMI_WINDOW_EXITING) &&
- !((vmcs12->cpu_based_vm_exec_control & CPU_BASED_INTR_WINDOW_EXITING) &&
- (vmcs12->guest_rflags & X86_EFLAGS_IF))) {
+ switch (vmcs12->guest_activity_state) {
+ case GUEST_ACTIVITY_HLT:
+ /*
+ * If we're entering a halted L2 vcpu and the L2 vcpu won't be
+ * awakened by event injection or by an NMI-window VM-exit or
+ * by an interrupt-window VM-exit, halt the vcpu.
+ */
+ if (!(vmcs12->vm_entry_intr_info_field & INTR_INFO_VALID_MASK) &&
+ !nested_cpu_has(vmcs12, CPU_BASED_NMI_WINDOW_EXITING) &&
+ !(nested_cpu_has(vmcs12, CPU_BASED_INTR_WINDOW_EXITING) &&
+ (vmcs12->guest_rflags & X86_EFLAGS_IF))) {
+ vmx->nested.nested_run_pending = 0;
+ return kvm_vcpu_halt(vcpu);
+ }
+ break;
+ case GUEST_ACTIVITY_WAIT_SIPI:
vmx->nested.nested_run_pending = 0;
- return kvm_vcpu_halt(vcpu);
+ vcpu->arch.mp_state = KVM_MP_STATE_INIT_RECEIVED;
+ break;
+ default:
+ break;
}
+
return 1;
vmentry_failed:
@@ -3797,7 +3808,20 @@ static int vmx_check_nested_events(struct kvm_vcpu *vcpu)
return -EBUSY;
nested_vmx_update_pending_dbg(vcpu);
clear_bit(KVM_APIC_INIT, &apic->pending_events);
- nested_vmx_vmexit(vcpu, EXIT_REASON_INIT_SIGNAL, 0, 0);
+ if (vcpu->arch.mp_state != KVM_MP_STATE_INIT_RECEIVED)
+ nested_vmx_vmexit(vcpu, EXIT_REASON_INIT_SIGNAL, 0, 0);
+ return 0;
+ }
+
+ if (lapic_in_kernel(vcpu) &&
+ test_bit(KVM_APIC_SIPI, &apic->pending_events)) {
+ if (block_nested_events)
+ return -EBUSY;
+
+ clear_bit(KVM_APIC_SIPI, &apic->pending_events);
+ if (vcpu->arch.mp_state == KVM_MP_STATE_INIT_RECEIVED)
+ nested_vmx_vmexit(vcpu, EXIT_REASON_SIPI_SIGNAL, 0,
+ apic->sipi_vector & 0xFFUL);
return 0;
}
@@ -4036,6 +4060,8 @@ static void sync_vmcs02_to_vmcs12(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
if (vcpu->arch.mp_state == KVM_MP_STATE_HALTED)
vmcs12->guest_activity_state = GUEST_ACTIVITY_HLT;
+ else if (vcpu->arch.mp_state == KVM_MP_STATE_INIT_RECEIVED)
+ vmcs12->guest_activity_state = GUEST_ACTIVITY_WAIT_SIPI;
else
vmcs12->guest_activity_state = GUEST_ACTIVITY_ACTIVE;
@@ -6483,7 +6509,8 @@ void nested_vmx_setup_ctls_msrs(struct nested_vmx_msrs *msrs, u32 ept_caps)
msrs->misc_low |=
MSR_IA32_VMX_MISC_VMWRITE_SHADOW_RO_FIELDS |
VMX_MISC_EMULATED_PREEMPTION_TIMER_RATE |
- VMX_MISC_ACTIVITY_HLT;
+ VMX_MISC_ACTIVITY_HLT |
+ VMX_MISC_ACTIVITY_WAIT_SIPI;
msrs->misc_high = 0;
/*
--
2.25.1