Commit cd7764fe9f73 ("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: Joao Martins <joao.m.martins@xxxxxxxxxx>
Co-developed-by: Nikita Leshenko <nikita.leshchenko@xxxxxxxxxx>
Signed-off-by: Nikita Leshenko <nikita.leshchenko@xxxxxxxxxx>
Signed-off-by: Liran Alon <liran.alon@xxxxxxxxxx>
---
arch/x86/include/asm/kvm_host.h | 2 ++
arch/x86/kvm/lapic.c | 11 +++++++----
arch/x86/kvm/svm.c | 20 ++++++++++++++++++++
arch/x86/kvm/vmx/nested.c | 14 ++++++++++++++
arch/x86/kvm/vmx/vmx.c | 6 ++++++
5 files changed, 49 insertions(+), 4 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 74e88e5edd9c..158483538181 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -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 {
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 685d17c11461..9620fe5ce8d1 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -2702,11 +2702,14 @@ 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.
+ * Because a CPU cannot be in these states immediately
+ * after it have processed an INIT signal (and thus in
+ * KVM_MP_STATE_INIT_RECEIVED state), just eat SIPIs
+ * and delay processing of INIT until CPU leaves
+ * the state which latch INIT signal.
*/
- if (is_smm(vcpu)) {
+ if (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);
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 6462c386015d..0e43acf7bea4 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -7205,6 +7205,24 @@ 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 INIT intercept, SVM should also implement
+ * kvm_x86_ops->check_nested_events() and process pending INIT
+ * signal to cause nested_svm_vmexit(). As SVM currently don't
+ * implement check_nested_events(), this work is delayed
+ * for future improvement.
+ */
+ return is_smm(vcpu) ||
+ !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,
@@ -7341,6 +7359,8 @@ 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)
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index ced9fba32598..d655fcd04c01 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -3401,6 +3401,15 @@ 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)) {
@@ -4466,7 +4475,12 @@ 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);
}
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index b5b5b2e5dac5..5a1aa0640f2a 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7479,6 +7479,11 @@ 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 is_smm(vcpu) || to_vmx(vcpu)->nested.vmxon;
+}
+
static __init int hardware_setup(void)
{
unsigned long host_bndcfgs;
@@ -7803,6 +7808,7 @@ 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)
--
2.20.1
