From bd17f417c07d4e1cbc85d7b69cd663725d12e8d6 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Fri, 4 Feb 2022 21:42:00 +0000 Subject: [PATCH] KVM: x86: WARN if KVM emulates an IPI without clearing the BUSY flag WARN if KVM emulates an IPI without clearing the BUSY flag, failure to do so could hang the guest if it waits for the IPI be sent. Opportunistically use APIC_ICR_BUSY macro instead of open coding the magic number, and add a comment to clarify why kvm_recalculate_apic_map() is unconditionally invoked (it's really, really confusing for IPIs due to the existence of fast paths that don't trigger a potential recalc). Signed-off-by: Sean Christopherson Message-Id: <20220204214205.3306634-7-seanjc@google.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/lapic.c | 10 +++++++++- arch/x86/kvm/x86.c | 9 ++++----- 2 files changed, 13 insertions(+), 6 deletions(-) diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index 2b5db46..90414c5 100644 --- a/arch/x86/kvm/lapic.c +++ b/arch/x86/kvm/lapic.c @@ -1275,6 +1275,9 @@ void kvm_apic_send_ipi(struct kvm_lapic *apic, u32 icr_low, u32 icr_high) { struct kvm_lapic_irq irq; + /* KVM has no delay and should always clear the BUSY/PENDING flag. */ + WARN_ON_ONCE(icr_low & APIC_ICR_BUSY); + irq.vector = icr_low & APIC_VECTOR_MASK; irq.delivery_mode = icr_low & APIC_MODE_MASK; irq.dest_mode = icr_low & APIC_DEST_MASK; @@ -2053,7 +2056,7 @@ int kvm_lapic_reg_write(struct kvm_lapic *apic, u32 reg, u32 val) } case APIC_ICR: /* No delay here, so we always clear the pending bit */ - val &= ~(1 << 12); + val &= ~APIC_ICR_BUSY; kvm_apic_send_ipi(apic, val, kvm_lapic_get_reg(apic, APIC_ICR2)); kvm_lapic_set_reg(apic, APIC_ICR, val); break; @@ -2131,6 +2134,11 @@ int kvm_lapic_reg_write(struct kvm_lapic *apic, u32 reg, u32 val) break; } + /* + * Recalculate APIC maps if necessary, e.g. if the software enable bit + * was toggled, the APIC ID changed, etc... The maps are marked dirty + * on relevant changes, i.e. this is a nop for most writes. + */ kvm_recalculate_apic_map(apic->vcpu->kvm); return ret; diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index d226012..7a8e875 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -2039,11 +2039,10 @@ static int handle_fastpath_set_x2apic_icr_irqoff(struct kvm_vcpu *vcpu, u64 data return 1; if (((data & APIC_SHORT_MASK) == APIC_DEST_NOSHORT) && - ((data & APIC_DEST_MASK) == APIC_DEST_PHYSICAL) && - ((data & APIC_MODE_MASK) == APIC_DM_FIXED) && - ((u32)(data >> 32) != X2APIC_BROADCAST)) { - - data &= ~(1 << 12); + ((data & APIC_DEST_MASK) == APIC_DEST_PHYSICAL) && + ((data & APIC_MODE_MASK) == APIC_DM_FIXED) && + ((u32)(data >> 32) != X2APIC_BROADCAST)) { + data &= ~APIC_ICR_BUSY; kvm_apic_send_ipi(vcpu->arch.apic, (u32)data, (u32)(data >> 32)); kvm_lapic_set_reg(vcpu->arch.apic, APIC_ICR2, (u32)(data >> 32)); kvm_lapic_set_reg(vcpu->arch.apic, APIC_ICR, (u32)data); -- 2.7.4