From: Marc Zyngier <marc.zyngier@arm.com> To: kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Cc: Eric Auger <eric.auger@redhat.com>, Christoffer Dall <cdall@kernel.org>, Shunyong Yang <shunyong.yang@hxt-semitech.com>, Andre Przywara <Andre.Przywara@arm.com> Subject: [PATCH v2] KVM: arm/arm64: vgic: Disallow Active+Pending for level interrupts Date: Fri, 16 Mar 2018 14:30:15 +0000 [thread overview] Message-ID: <20180316143015.32055-1-marc.zyngier@arm.com> (raw) It was recently reported that VFIO mediated devices, and anything that VFIO exposes as level interrupts, do no strictly follow the expected logic of such interrupts as it only lowers the input line when the guest has EOId the interrupt at the GIC level, rather than when it Acked the interrupt at the device level. THe GIC's Active+Pending state is fundamentally incompatible with this behaviour, as it prevents KVM from observing the EOI, and in turn results in VFIO never dropping the line. This results in an interrupt storm in the guest, which it really never expected. As we cannot really change VFIO to follow the strict rules of level signalling, let's forbid the A+P state altogether, as it is in the end only an optimization. It ensures that we will transition via an invalid state, which we can use to notify VFIO of the EOI. Signed-off-by: Marc Zyngier <marc.zyngier@arm.com> --- - From v1: * Only clear the latch when going via an invalid state virt/kvm/arm/vgic/vgic-v2.c | 54 +++++++++++++++++++++++++-------------------- virt/kvm/arm/vgic/vgic-v3.c | 54 +++++++++++++++++++++++++-------------------- 2 files changed, 60 insertions(+), 48 deletions(-) diff --git a/virt/kvm/arm/vgic/vgic-v2.c b/virt/kvm/arm/vgic/vgic-v2.c index 29556f71b691..8427586760fc 100644 --- a/virt/kvm/arm/vgic/vgic-v2.c +++ b/virt/kvm/arm/vgic/vgic-v2.c @@ -105,12 +105,9 @@ void vgic_v2_fold_lr_state(struct kvm_vcpu *vcpu) /* * Clear soft pending state when level irqs have been acked. - * Always regenerate the pending state. */ - if (irq->config == VGIC_CONFIG_LEVEL) { - if (!(val & GICH_LR_PENDING_BIT)) - irq->pending_latch = false; - } + if (irq->config == VGIC_CONFIG_LEVEL && !(val & GICH_LR_STATE)) + irq->pending_latch = false; /* * Level-triggered mapped IRQs are special because we only @@ -153,8 +150,35 @@ void vgic_v2_fold_lr_state(struct kvm_vcpu *vcpu) void vgic_v2_populate_lr(struct kvm_vcpu *vcpu, struct vgic_irq *irq, int lr) { u32 val = irq->intid; + bool allow_pending = true; + + if (irq->active) + val |= GICH_LR_ACTIVE_BIT; + + if (irq->hw) { + val |= GICH_LR_HW; + val |= irq->hwintid << GICH_LR_PHYSID_CPUID_SHIFT; + /* + * Never set pending+active on a HW interrupt, as the + * pending state is kept at the physical distributor + * level. + */ + if (irq->active) + allow_pending = false; + } else { + if (irq->config == VGIC_CONFIG_LEVEL) { + val |= GICH_LR_EOI; - if (irq_is_pending(irq)) { + /* + * Software resampling doesn't work very well + * if we allow P+A, so let's not do that. + */ + if (irq->active) + allow_pending = false; + } + } + + if (allow_pending && irq_is_pending(irq)) { val |= GICH_LR_PENDING_BIT; if (irq->config == VGIC_CONFIG_EDGE) @@ -171,24 +195,6 @@ void vgic_v2_populate_lr(struct kvm_vcpu *vcpu, struct vgic_irq *irq, int lr) } } - if (irq->active) - val |= GICH_LR_ACTIVE_BIT; - - if (irq->hw) { - val |= GICH_LR_HW; - val |= irq->hwintid << GICH_LR_PHYSID_CPUID_SHIFT; - /* - * Never set pending+active on a HW interrupt, as the - * pending state is kept at the physical distributor - * level. - */ - if (irq->active && irq_is_pending(irq)) - val &= ~GICH_LR_PENDING_BIT; - } else { - if (irq->config == VGIC_CONFIG_LEVEL) - val |= GICH_LR_EOI; - } - /* * Level-triggered mapped IRQs are special because we only observe * rising edges as input to the VGIC. We therefore lower the line diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c index 0ff2006f3781..dd984f726805 100644 --- a/virt/kvm/arm/vgic/vgic-v3.c +++ b/virt/kvm/arm/vgic/vgic-v3.c @@ -96,12 +96,9 @@ void vgic_v3_fold_lr_state(struct kvm_vcpu *vcpu) /* * Clear soft pending state when level irqs have been acked. - * Always regenerate the pending state. */ - if (irq->config == VGIC_CONFIG_LEVEL) { - if (!(val & ICH_LR_PENDING_BIT)) - irq->pending_latch = false; - } + if (irq->config == VGIC_CONFIG_LEVEL && !(val & ICH_LR_STATE)) + irq->pending_latch = false; /* * Level-triggered mapped IRQs are special because we only @@ -135,8 +132,35 @@ void vgic_v3_populate_lr(struct kvm_vcpu *vcpu, struct vgic_irq *irq, int lr) { u32 model = vcpu->kvm->arch.vgic.vgic_model; u64 val = irq->intid; + bool allow_pending = true; + + if (irq->active) + val |= ICH_LR_ACTIVE_BIT; + + if (irq->hw) { + val |= ICH_LR_HW; + val |= ((u64)irq->hwintid) << ICH_LR_PHYS_ID_SHIFT; + /* + * Never set pending+active on a HW interrupt, as the + * pending state is kept at the physical distributor + * level. + */ + if (irq->active) + allow_pending = false; + } else { + if (irq->config == VGIC_CONFIG_LEVEL) { + val |= ICH_LR_EOI; - if (irq_is_pending(irq)) { + /* + * Software resampling doesn't work very well + * if we allow P+A, so let's not do that. + */ + if (irq->active) + allow_pending = false; + } + } + + if (allow_pending && irq_is_pending(irq)) { val |= ICH_LR_PENDING_BIT; if (irq->config == VGIC_CONFIG_EDGE) @@ -154,24 +178,6 @@ void vgic_v3_populate_lr(struct kvm_vcpu *vcpu, struct vgic_irq *irq, int lr) } } - if (irq->active) - val |= ICH_LR_ACTIVE_BIT; - - if (irq->hw) { - val |= ICH_LR_HW; - val |= ((u64)irq->hwintid) << ICH_LR_PHYS_ID_SHIFT; - /* - * Never set pending+active on a HW interrupt, as the - * pending state is kept at the physical distributor - * level. - */ - if (irq->active && irq_is_pending(irq)) - val &= ~ICH_LR_PENDING_BIT; - } else { - if (irq->config == VGIC_CONFIG_LEVEL) - val |= ICH_LR_EOI; - } - /* * Level-triggered mapped IRQs are special because we only observe * rising edges as input to the VGIC. We therefore lower the line -- 2.14.2
WARNING: multiple messages have this Message-ID (diff)
From: marc.zyngier@arm.com (Marc Zyngier) To: linux-arm-kernel@lists.infradead.org Subject: [PATCH v2] KVM: arm/arm64: vgic: Disallow Active+Pending for level interrupts Date: Fri, 16 Mar 2018 14:30:15 +0000 [thread overview] Message-ID: <20180316143015.32055-1-marc.zyngier@arm.com> (raw) It was recently reported that VFIO mediated devices, and anything that VFIO exposes as level interrupts, do no strictly follow the expected logic of such interrupts as it only lowers the input line when the guest has EOId the interrupt at the GIC level, rather than when it Acked the interrupt at the device level. THe GIC's Active+Pending state is fundamentally incompatible with this behaviour, as it prevents KVM from observing the EOI, and in turn results in VFIO never dropping the line. This results in an interrupt storm in the guest, which it really never expected. As we cannot really change VFIO to follow the strict rules of level signalling, let's forbid the A+P state altogether, as it is in the end only an optimization. It ensures that we will transition via an invalid state, which we can use to notify VFIO of the EOI. Signed-off-by: Marc Zyngier <marc.zyngier@arm.com> --- - From v1: * Only clear the latch when going via an invalid state virt/kvm/arm/vgic/vgic-v2.c | 54 +++++++++++++++++++++++++-------------------- virt/kvm/arm/vgic/vgic-v3.c | 54 +++++++++++++++++++++++++-------------------- 2 files changed, 60 insertions(+), 48 deletions(-) diff --git a/virt/kvm/arm/vgic/vgic-v2.c b/virt/kvm/arm/vgic/vgic-v2.c index 29556f71b691..8427586760fc 100644 --- a/virt/kvm/arm/vgic/vgic-v2.c +++ b/virt/kvm/arm/vgic/vgic-v2.c @@ -105,12 +105,9 @@ void vgic_v2_fold_lr_state(struct kvm_vcpu *vcpu) /* * Clear soft pending state when level irqs have been acked. - * Always regenerate the pending state. */ - if (irq->config == VGIC_CONFIG_LEVEL) { - if (!(val & GICH_LR_PENDING_BIT)) - irq->pending_latch = false; - } + if (irq->config == VGIC_CONFIG_LEVEL && !(val & GICH_LR_STATE)) + irq->pending_latch = false; /* * Level-triggered mapped IRQs are special because we only @@ -153,8 +150,35 @@ void vgic_v2_fold_lr_state(struct kvm_vcpu *vcpu) void vgic_v2_populate_lr(struct kvm_vcpu *vcpu, struct vgic_irq *irq, int lr) { u32 val = irq->intid; + bool allow_pending = true; + + if (irq->active) + val |= GICH_LR_ACTIVE_BIT; + + if (irq->hw) { + val |= GICH_LR_HW; + val |= irq->hwintid << GICH_LR_PHYSID_CPUID_SHIFT; + /* + * Never set pending+active on a HW interrupt, as the + * pending state is kept@the physical distributor + * level. + */ + if (irq->active) + allow_pending = false; + } else { + if (irq->config == VGIC_CONFIG_LEVEL) { + val |= GICH_LR_EOI; - if (irq_is_pending(irq)) { + /* + * Software resampling doesn't work very well + * if we allow P+A, so let's not do that. + */ + if (irq->active) + allow_pending = false; + } + } + + if (allow_pending && irq_is_pending(irq)) { val |= GICH_LR_PENDING_BIT; if (irq->config == VGIC_CONFIG_EDGE) @@ -171,24 +195,6 @@ void vgic_v2_populate_lr(struct kvm_vcpu *vcpu, struct vgic_irq *irq, int lr) } } - if (irq->active) - val |= GICH_LR_ACTIVE_BIT; - - if (irq->hw) { - val |= GICH_LR_HW; - val |= irq->hwintid << GICH_LR_PHYSID_CPUID_SHIFT; - /* - * Never set pending+active on a HW interrupt, as the - * pending state is kept@the physical distributor - * level. - */ - if (irq->active && irq_is_pending(irq)) - val &= ~GICH_LR_PENDING_BIT; - } else { - if (irq->config == VGIC_CONFIG_LEVEL) - val |= GICH_LR_EOI; - } - /* * Level-triggered mapped IRQs are special because we only observe * rising edges as input to the VGIC. We therefore lower the line diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c index 0ff2006f3781..dd984f726805 100644 --- a/virt/kvm/arm/vgic/vgic-v3.c +++ b/virt/kvm/arm/vgic/vgic-v3.c @@ -96,12 +96,9 @@ void vgic_v3_fold_lr_state(struct kvm_vcpu *vcpu) /* * Clear soft pending state when level irqs have been acked. - * Always regenerate the pending state. */ - if (irq->config == VGIC_CONFIG_LEVEL) { - if (!(val & ICH_LR_PENDING_BIT)) - irq->pending_latch = false; - } + if (irq->config == VGIC_CONFIG_LEVEL && !(val & ICH_LR_STATE)) + irq->pending_latch = false; /* * Level-triggered mapped IRQs are special because we only @@ -135,8 +132,35 @@ void vgic_v3_populate_lr(struct kvm_vcpu *vcpu, struct vgic_irq *irq, int lr) { u32 model = vcpu->kvm->arch.vgic.vgic_model; u64 val = irq->intid; + bool allow_pending = true; + + if (irq->active) + val |= ICH_LR_ACTIVE_BIT; + + if (irq->hw) { + val |= ICH_LR_HW; + val |= ((u64)irq->hwintid) << ICH_LR_PHYS_ID_SHIFT; + /* + * Never set pending+active on a HW interrupt, as the + * pending state is kept@the physical distributor + * level. + */ + if (irq->active) + allow_pending = false; + } else { + if (irq->config == VGIC_CONFIG_LEVEL) { + val |= ICH_LR_EOI; - if (irq_is_pending(irq)) { + /* + * Software resampling doesn't work very well + * if we allow P+A, so let's not do that. + */ + if (irq->active) + allow_pending = false; + } + } + + if (allow_pending && irq_is_pending(irq)) { val |= ICH_LR_PENDING_BIT; if (irq->config == VGIC_CONFIG_EDGE) @@ -154,24 +178,6 @@ void vgic_v3_populate_lr(struct kvm_vcpu *vcpu, struct vgic_irq *irq, int lr) } } - if (irq->active) - val |= ICH_LR_ACTIVE_BIT; - - if (irq->hw) { - val |= ICH_LR_HW; - val |= ((u64)irq->hwintid) << ICH_LR_PHYS_ID_SHIFT; - /* - * Never set pending+active on a HW interrupt, as the - * pending state is kept@the physical distributor - * level. - */ - if (irq->active && irq_is_pending(irq)) - val &= ~ICH_LR_PENDING_BIT; - } else { - if (irq->config == VGIC_CONFIG_LEVEL) - val |= ICH_LR_EOI; - } - /* * Level-triggered mapped IRQs are special because we only observe * rising edges as input to the VGIC. We therefore lower the line -- 2.14.2
next reply other threads:[~2018-03-16 14:30 UTC|newest] Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-03-16 14:30 Marc Zyngier [this message] 2018-03-16 14:30 ` [PATCH v2] KVM: arm/arm64: vgic: Disallow Active+Pending for level interrupts Marc Zyngier 2018-03-20 14:25 ` Auger Eric 2018-03-20 14:25 ` Auger Eric 2018-03-21 1:20 ` [此邮件可能存在风险] " Yang, Shunyong 2018-03-21 1:20 ` Yang, Shunyong
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