Commit 4b9852f4 authored by Liran Alon's avatar Liran Alon Committed by Paolo Bonzini
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KVM: x86: Fix INIT signal handling in various CPU states 



Commit cd7764fe ("KVM: x86: latch INITs while in system management mode")
changed code to latch INIT while vCPU is in SMM and process latched INIT
when leaving SMM. It left a subtle remark in commit message that similar
treatment should also be done while vCPU is in VMX non-root-mode.

However, INIT signals should actually be latched in various vCPU states:
(*) For both Intel and AMD, INIT signals should be latched while vCPU
is in SMM.
(*) For Intel, INIT should also be latched while vCPU is in VMX
operation and later processed when vCPU leaves VMX operation by
executing VMXOFF.
(*) For AMD, INIT should also be latched while vCPU runs with GIF=0
or in guest-mode with intercept defined on INIT signal.

To fix this:
1) Add kvm_x86_ops->apic_init_signal_blocked() such that each CPU vendor
can define the various CPU states in which INIT signals should be
blocked and modify kvm_apic_accept_events() to use it.
2) Modify vmx_check_nested_events() to check for pending INIT signal
while vCPU in guest-mode. If so, emualte vmexit on
EXIT_REASON_INIT_SIGNAL. Note that nSVM should have similar behaviour
but is currently left as a TODO comment to implement in the future
because nSVM don't yet implement svm_check_nested_events().

Note: Currently KVM nVMX implementation don't support VMX wait-for-SIPI
activity state as specified in MSR_IA32_VMX_MISC bits 6:8 exposed to
guest (See nested_vmx_setup_ctls_msrs()).
If and when support for this activity state will be implemented,
kvm_check_nested_events() would need to avoid emulating vmexit on
INIT signal in case activity-state is wait-for-SIPI. In addition,
kvm_apic_accept_events() would need to be modified to avoid discarding
SIPI in case VMX activity-state is wait-for-SIPI but instead delay
SIPI processing to vmx_check_nested_events() that would clear
pending APIC events and emulate vmexit on SIPI.

Reviewed-by: default avatarJoao Martins <joao.m.martins@oracle.com>
Co-developed-by: default avatarNikita Leshenko <nikita.leshchenko@oracle.com>
Signed-off-by: default avatarNikita Leshenko <nikita.leshchenko@oracle.com>
Signed-off-by: default avatarLiran Alon <liran.alon@oracle.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 4a53d99d

arch/x86/include/asm/kvm_host.h

+2 −0
Original line number Diff line number Diff line
@@ -1209,6 +1209,8 @@ struct kvm_x86_ops { 
	uint16_t (*nested_get_evmcs_version)(struct kvm_vcpu *vcpu);



	bool (*need_emulation_on_page_fault)(struct kvm_vcpu *vcpu);



	bool (*apic_init_signal_blocked)(struct kvm_vcpu *vcpu);

};



struct kvm_arch_async_pf {

arch/x86/kvm/lapic.c

+7 −4
Original line number Diff line number Diff line
@@ -2706,11 +2706,14 @@ void kvm_apic_accept_events(struct kvm_vcpu *vcpu) 
		return;



	/*

	 * INITs are latched while in SMM.  Because an SMM CPU cannot

	 * be in KVM_MP_STATE_INIT_RECEIVED state, just eat SIPIs

	 * and delay processing of INIT until the next RSM.

	 * INITs are latched while CPU is in specific states

	 * (SMM, VMX non-root mode, SVM with GIF=0).

	 * Because a CPU cannot be in these states immediately

	 * after it has processed an INIT signal (and thus in

	 * KVM_MP_STATE_INIT_RECEIVED state), just eat SIPIs

	 * and leave the INIT pending.

	 */

	if (is_smm(vcpu)) {

	if (is_smm(vcpu) || kvm_x86_ops->apic_init_signal_blocked(vcpu)) {

		WARN_ON_ONCE(vcpu->arch.mp_state == KVM_MP_STATE_INIT_RECEIVED);

		if (test_bit(KVM_APIC_SIPI, &apic->pending_events))

			clear_bit(KVM_APIC_SIPI, &apic->pending_events);

arch/x86/kvm/svm.c

+17 −0
Original line number Diff line number Diff line
@@ -7170,6 +7170,21 @@ static bool svm_need_emulation_on_page_fault(struct kvm_vcpu *vcpu) 
	return false;

}



static bool svm_apic_init_signal_blocked(struct kvm_vcpu *vcpu)

{

	struct vcpu_svm *svm = to_svm(vcpu);



	/*

	 * TODO: Last condition latch INIT signals on vCPU when

	 * vCPU is in guest-mode and vmcb12 defines intercept on INIT.

	 * To properly emulate the INIT intercept, SVM should implement

	 * kvm_x86_ops->check_nested_events() and call nested_svm_vmexit()

	 * there if an INIT signal is pending.

	 */

	return !gif_set(svm) ||

		   (svm->vmcb->control.intercept & (1ULL << INTERCEPT_INIT));

}



static struct kvm_x86_ops svm_x86_ops __ro_after_init = {

	.cpu_has_kvm_support = has_svm,

	.disabled_by_bios = is_disabled,
@@ -7306,6 +7321,8 @@ static struct kvm_x86_ops svm_x86_ops __ro_after_init = { 
	.nested_get_evmcs_version = nested_get_evmcs_version,



	.need_emulation_on_page_fault = svm_need_emulation_on_page_fault,



	.apic_init_signal_blocked = svm_apic_init_signal_blocked,

};



static int __init svm_init(void)

arch/x86/kvm/vmx/nested.c

+14 −0
Original line number Diff line number Diff line
@@ -3409,6 +3409,15 @@ static int vmx_check_nested_events(struct kvm_vcpu *vcpu, bool external_intr) 
	unsigned long exit_qual;

	bool block_nested_events =

	    vmx->nested.nested_run_pending || kvm_event_needs_reinjection(vcpu);

	struct kvm_lapic *apic = vcpu->arch.apic;



	if (lapic_in_kernel(vcpu) &&

		test_bit(KVM_APIC_INIT, &apic->pending_events)) {

		if (block_nested_events)

			return -EBUSY;

		nested_vmx_vmexit(vcpu, EXIT_REASON_INIT_SIGNAL, 0, 0);

		return 0;

	}



	if (vcpu->arch.exception.pending &&

		nested_vmx_check_exception(vcpu, &exit_qual)) {
@@ -4470,7 +4479,12 @@ static int handle_vmoff(struct kvm_vcpu *vcpu) 
{

	if (!nested_vmx_check_permission(vcpu))

		return 1;



	free_nested(vcpu);



	/* Process a latched INIT during time CPU was in VMX operation */

	kvm_make_request(KVM_REQ_EVENT, vcpu);



	return nested_vmx_succeed(vcpu);

}

arch/x86/kvm/vmx/vmx.c

+6 −0
Original line number Diff line number Diff line
@@ -7470,6 +7470,11 @@ static bool vmx_need_emulation_on_page_fault(struct kvm_vcpu *vcpu) 
	return false;

}



static bool vmx_apic_init_signal_blocked(struct kvm_vcpu *vcpu)

{

	return to_vmx(vcpu)->nested.vmxon;

}



static __init int hardware_setup(void)

{

	unsigned long host_bndcfgs;
@@ -7794,6 +7799,7 @@ static struct kvm_x86_ops vmx_x86_ops __ro_after_init = { 
	.get_vmcs12_pages = NULL,

	.nested_enable_evmcs = NULL,

	.need_emulation_on_page_fault = vmx_need_emulation_on_page_fault,

	.apic_init_signal_blocked = vmx_apic_init_signal_blocked,

};



static void vmx_cleanup_l1d_flush(void)

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