Commit bf0cd88c authored by Yadong Qi's avatar Yadong Qi Committed by Paolo Bonzini
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KVM: x86: emulate wait-for-SIPI and SIPI-VMExit 



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: default avatarYadong Qi <yadong.qi@intel.com>
Message-Id: <20200922052343.84388-1-yadong.qi@intel.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Message-Id: <20201106065122.403183-1-yadong.qi@intel.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 1c96dcce

arch/x86/include/asm/vmx.h

+1 −0
Original line number Diff line number Diff line
@@ -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

arch/x86/include/uapi/asm/vmx.h

+2 −0
Original line number Diff line number Diff line
@@ -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" }, \

arch/x86/kvm/vmx/nested.c

+41 −14
Original line number Diff line number Diff line
@@ -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);



	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->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) &&

		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;

		vcpu->arch.mp_state = KVM_MP_STATE_INIT_RECEIVED;

		break;

	default:

		break;

	}



	return 1;



vmentry_failed:
@@ -3797,10 +3808,23 @@ 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);

		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;

	}



	/*

	 * Process any exceptions that are not debug traps before MTF.

	 */
@@ -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;



	/*

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