From 4b9852f4f38909a9ca74e71afb35aafba0871aa1 Mon Sep 17 00:00:00 2001 From: Liran Alon Date: Mon, 26 Aug 2019 13:24:49 +0300 Subject: KVM: x86: Fix INIT signal handling in various CPU states 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 Co-developed-by: Nikita Leshenko Signed-off-by: Nikita Leshenko Signed-off-by: Liran Alon Signed-off-by: Paolo Bonzini --- arch/x86/kvm/lapic.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) (limited to 'arch/x86/kvm/lapic.c') diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index 559e1c4c0832..dbbe4781fbb2 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -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); -- cgit v1.2.3-59-g8ed1b