From 4b9852f4f38909a9ca74e71afb35aafba0871aa1 Mon Sep 17 00:00:00 2001 From: Liran Alon Date: Mon, 26 Aug 2019 13:24:49 +0300 Subject: [PATCH] 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/include/asm/kvm_host.h | 2 ++ arch/x86/kvm/lapic.c | 11 +++++++---- arch/x86/kvm/svm.c | 17 +++++++++++++++++ arch/x86/kvm/vmx/nested.c | 14 ++++++++++++++ arch/x86/kvm/vmx/vmx.c | 6 ++++++ 5 files changed, 46 insertions(+), 4 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index c4f271a9b306..b523949a8df8 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 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); diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index 2854aafc489e..d24050b647c7 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -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) diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c index ad2453317c4b..6ce83c602e7f 100644 --- a/arch/x86/kvm/vmx/nested.c +++ b/arch/x86/kvm/vmx/nested.c @@ -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); } diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 99f52f8c969a..73bf9a2e6fb6 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -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) -- GitLab