>From 7e41f58f1ce591bf5a40a94993957879a60103d6 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Wed, 20 Oct 2021 14:44:14 +0200 Subject: [PATCH 2/2] KVM: SVM: Add support to handle AP reset MSR protocol From: Tom Lendacky Add support for AP Reset Hold being invoked using the GHCB MSR protocol, available in version 2 of the GHCB specification. Signed-off-by: Tom Lendacky Signed-off-by: Brijesh Singh Signed-off-by: Joerg Roedel Co-developed-by: Sean Christopherson Signed-off-by: Sean Christopherson --- arch/x86/kvm/svm/sev.c | 53 +++++++++++++++++++++++++++++++++++++----- arch/x86/kvm/svm/svm.h | 1 + 2 files changed, 48 insertions(+), 6 deletions(-) diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index f8dfa88993b8..1174270d18ee 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -2405,10 +2405,36 @@ static u64 ghcb_msr_version_info(void) return msr; } -static int sev_emulate_ap_reset_hold(struct vcpu_svm *svm) + +static u64 ghcb_msr_ap_rst_resp(u64 value) +{ + return (u64)GHCB_MSR_AP_RESET_HOLD_RESP | (value << GHCB_DATA_LOW); +} + +static int sev_emulate_ap_reset_hold(struct vcpu_svm *svm, u64 hold_type) { int ret = kvm_skip_emulated_instruction(&svm->vcpu); + if (hold_type == GHCB_MSR_AP_RESET_HOLD_REQ) { + /* + * Preset the result to a non-SIPI return and then only set + * the result to non-zero when delivering a SIPI. + */ + svm->vmcb->control.ghcb_gpa = ghcb_msr_ap_rst_resp(0); + svm->reset_hold_msr_protocol = true; + } else { + WARN_ON_ONCE(hold_type != SVM_VMGEXIT_AP_HLT_LOOP); + svm->reset_hold_msr_protocol = false; + } + + /* + * Ensure the writes to ghcb_gpa and reset_hold_msr_protocol are visible + * before the MP state change so that the INIT-SIPI doesn't misread + * reset_hold_msr_protocol or write ghcb_gpa before this. Pairs with + * the smp_rmb() in sev_vcpu_reset(). + */ + smp_wmb(); + return __kvm_vcpu_halt(&svm->vcpu, KVM_MP_STATE_AP_RESET_HOLD, KVM_EXIT_AP_RESET_HOLD) && ret; } @@ -2459,6 +2485,9 @@ static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm) break; } + case GHCB_MSR_AP_RESET_HOLD_REQ: + ret = sev_emulate_ap_reset_hold(svm, GHCB_MSR_AP_RESET_HOLD_REQ); + break; case GHCB_MSR_TERM_REQ: { u64 reason_set, reason_code; @@ -2544,7 +2573,7 @@ int sev_handle_vmgexit(struct kvm_vcpu *vcpu) ret = svm_invoke_exit_handler(vcpu, SVM_EXIT_IRET); break; case SVM_VMGEXIT_AP_HLT_LOOP: - ret = sev_emulate_ap_reset_hold(svm); + ret = sev_emulate_ap_reset_hold(svm, SVM_VMGEXIT_AP_HLT_LOOP); break; case SVM_VMGEXIT_AP_JUMP_TABLE: { struct kvm_sev_info *sev = &to_kvm_svm(vcpu->kvm)->sev_info; @@ -2642,11 +2671,23 @@ void sev_es_vcpu_reset(struct vcpu_svm *svm, bool init_event) if (init_event) { /* * If the vCPU is in a "reset" hold, signal via SW_EXIT_INFO_2 - * that, assuming it receives a SIPI, the vCPU was "released". + * (or the GHCB_GPA for the MSR protocol) that, assuming it + * receives a SIPI, the vCPU was "released". */ - if (svm->vcpu.arch.mp_state == KVM_MP_STATE_AP_RESET_HOLD && - svm->ghcb) - ghcb_set_sw_exit_info_2(svm->ghcb, 1); + if (svm->vcpu.arch.mp_state == KVM_MP_STATE_AP_RESET_HOLD) { + /* + * Ensure mp_state is read before reset_hold_msr_protocol + * and before writing ghcb_gpa to ensure KVM conumes the + * correct protocol. Pairs with the smp_wmb() in + * sev_emulate_ap_reset_hold(). + */ + smp_rmb(); + if (svm->reset_hold_msr_protocol) + svm->vmcb->control.ghcb_gpa = ghcb_msr_ap_rst_resp(1); + else if (svm->ghcb) + ghcb_set_sw_exit_info_2(svm->ghcb, 1); + svm->reset_hold_msr_protocol = false; + } return; } diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h index c1f3685db2e1..531d3258df58 100644 --- a/arch/x86/kvm/svm/svm.h +++ b/arch/x86/kvm/svm/svm.h @@ -198,6 +198,7 @@ struct vcpu_svm { bool ghcb_sa_free; bool guest_state_loaded; + bool reset_hold_msr_protocol; }; struct svm_cpu_data { -- 2.33.0.1079.g6e70778dc9-goog