On 17/04/2020 09:33, Marc Zyngier wrote:
> When a guest tries to read the active state of its interrupts,
> we currently just return whatever state we have in memory. This
> means that if such an interrupt lives in a List Register on another
> CPU, we fail to obsertve the latest active state for this interrupt.
>
> In order to remedy this, stop all the other vcpus so that they exit
> and we can observe the most recent value for the state. This is
> similar to what we are doing for the write side of the same
> registers, and results in new MMIO handlers for userspace (which
> do not need to stop the guest, as it is supposed to be stopped
> already).
Thanks for the changes! Checked for other users of VGIC_NR_PRIVATE_IRQS,
also for not missing other ACTIVE bit register handlers.
Looks good to me!
>
> Reported-by: Julien Grall <julien@xxxxxxx>
> Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
Reviewed-by: Andre Przywara <andre.przywara@xxxxxxx>
Cheers,
Andre
> ---
> virt/kvm/arm/vgic/vgic-mmio-v2.c | 4 +-
> virt/kvm/arm/vgic/vgic-mmio-v3.c | 12 ++--
> virt/kvm/arm/vgic/vgic-mmio.c | 100 ++++++++++++++++++++-----------
> virt/kvm/arm/vgic/vgic-mmio.h | 3 +
> 4 files changed, 75 insertions(+), 44 deletions(-)
>
> diff --git a/virt/kvm/arm/vgic/vgic-mmio-v2.c b/virt/kvm/arm/vgic/vgic-mmio-v2.c
> index 5945f062d749..d63881f60e1a 100644
> --- a/virt/kvm/arm/vgic/vgic-mmio-v2.c
> +++ b/virt/kvm/arm/vgic/vgic-mmio-v2.c
> @@ -422,11 +422,11 @@ static const struct vgic_register_region vgic_v2_dist_registers[] = {
> VGIC_ACCESS_32bit),
> REGISTER_DESC_WITH_BITS_PER_IRQ(GIC_DIST_ACTIVE_SET,
> vgic_mmio_read_active, vgic_mmio_write_sactive,
> - NULL, vgic_mmio_uaccess_write_sactive, 1,
> + vgic_uaccess_read_active, vgic_mmio_uaccess_write_sactive, 1,
> VGIC_ACCESS_32bit),
> REGISTER_DESC_WITH_BITS_PER_IRQ(GIC_DIST_ACTIVE_CLEAR,
> vgic_mmio_read_active, vgic_mmio_write_cactive,
> - NULL, vgic_mmio_uaccess_write_cactive, 1,
> + vgic_uaccess_read_active, vgic_mmio_uaccess_write_cactive, 1,
> VGIC_ACCESS_32bit),
> REGISTER_DESC_WITH_BITS_PER_IRQ(GIC_DIST_PRI,
> vgic_mmio_read_priority, vgic_mmio_write_priority, NULL, NULL,
> diff --git a/virt/kvm/arm/vgic/vgic-mmio-v3.c b/virt/kvm/arm/vgic/vgic-mmio-v3.c
> index e72dcc454247..f2b37a081f26 100644
> --- a/virt/kvm/arm/vgic/vgic-mmio-v3.c
> +++ b/virt/kvm/arm/vgic/vgic-mmio-v3.c
> @@ -553,11 +553,11 @@ static const struct vgic_register_region vgic_v3_dist_registers[] = {
> VGIC_ACCESS_32bit),
> REGISTER_DESC_WITH_BITS_PER_IRQ_SHARED(GICD_ISACTIVER,
> vgic_mmio_read_active, vgic_mmio_write_sactive,
> - NULL, vgic_mmio_uaccess_write_sactive, 1,
> + vgic_uaccess_read_active, vgic_mmio_uaccess_write_sactive, 1,
> VGIC_ACCESS_32bit),
> REGISTER_DESC_WITH_BITS_PER_IRQ_SHARED(GICD_ICACTIVER,
> vgic_mmio_read_active, vgic_mmio_write_cactive,
> - NULL, vgic_mmio_uaccess_write_cactive,
> + vgic_uaccess_read_active, vgic_mmio_uaccess_write_cactive,
> 1, VGIC_ACCESS_32bit),
> REGISTER_DESC_WITH_BITS_PER_IRQ_SHARED(GICD_IPRIORITYR,
> vgic_mmio_read_priority, vgic_mmio_write_priority, NULL, NULL,
> @@ -625,12 +625,12 @@ static const struct vgic_register_region vgic_v3_rd_registers[] = {
> VGIC_ACCESS_32bit),
> REGISTER_DESC_WITH_LENGTH_UACCESS(SZ_64K + GICR_ISACTIVER0,
> vgic_mmio_read_active, vgic_mmio_write_sactive,
> - NULL, vgic_mmio_uaccess_write_sactive,
> - 4, VGIC_ACCESS_32bit),
> + vgic_uaccess_read_active, vgic_mmio_uaccess_write_sactive, 4,
> + VGIC_ACCESS_32bit),
> REGISTER_DESC_WITH_LENGTH_UACCESS(SZ_64K + GICR_ICACTIVER0,
> vgic_mmio_read_active, vgic_mmio_write_cactive,
> - NULL, vgic_mmio_uaccess_write_cactive,
> - 4, VGIC_ACCESS_32bit),
> + vgic_uaccess_read_active, vgic_mmio_uaccess_write_cactive, 4,
> + VGIC_ACCESS_32bit),
> REGISTER_DESC_WITH_LENGTH(SZ_64K + GICR_IPRIORITYR0,
> vgic_mmio_read_priority, vgic_mmio_write_priority, 32,
> VGIC_ACCESS_32bit | VGIC_ACCESS_8bit),
> diff --git a/virt/kvm/arm/vgic/vgic-mmio.c b/virt/kvm/arm/vgic/vgic-mmio.c
> index d085e047953f..b38e94e8f74a 100644
> --- a/virt/kvm/arm/vgic/vgic-mmio.c
> +++ b/virt/kvm/arm/vgic/vgic-mmio.c
> @@ -348,8 +348,39 @@ void vgic_mmio_write_cpending(struct kvm_vcpu *vcpu,
> }
> }
>
> -unsigned long vgic_mmio_read_active(struct kvm_vcpu *vcpu,
> - gpa_t addr, unsigned int len)
> +
> +/*
> + * If we are fiddling with an IRQ's active state, we have to make sure the IRQ
> + * is not queued on some running VCPU's LRs, because then the change to the
> + * active state can be overwritten when the VCPU's state is synced coming back
> + * from the guest.
> + *
> + * For shared interrupts as well as GICv3 private interrupts, we have to
> + * stop all the VCPUs because interrupts can be migrated while we don't hold
> + * the IRQ locks and we don't want to be chasing moving targets.
> + *
> + * For GICv2 private interrupts we don't have to do anything because
> + * userspace accesses to the VGIC state already require all VCPUs to be
> + * stopped, and only the VCPU itself can modify its private interrupts
> + * active state, which guarantees that the VCPU is not running.
> + */
> +static void vgic_access_active_prepare(struct kvm_vcpu *vcpu, u32 intid)
> +{
> + if (vcpu->kvm->arch.vgic.vgic_model == KVM_DEV_TYPE_ARM_VGIC_V3 ||
> + intid >= VGIC_NR_PRIVATE_IRQS)
> + kvm_arm_halt_guest(vcpu->kvm);
> +}
> +
> +/* See vgic_access_active_prepare */
> +static void vgic_access_active_finish(struct kvm_vcpu *vcpu, u32 intid)
> +{
> + if (vcpu->kvm->arch.vgic.vgic_model == KVM_DEV_TYPE_ARM_VGIC_V3 ||
> + intid >= VGIC_NR_PRIVATE_IRQS)
> + kvm_arm_resume_guest(vcpu->kvm);
> +}
> +
> +static unsigned long __vgic_mmio_read_active(struct kvm_vcpu *vcpu,
> + gpa_t addr, unsigned int len)
> {
> u32 intid = VGIC_ADDR_TO_INTID(addr, 1);
> u32 value = 0;
> @@ -359,6 +390,10 @@ unsigned long vgic_mmio_read_active(struct kvm_vcpu *vcpu,
> for (i = 0; i < len * 8; i++) {
> struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);
>
> + /*
> + * Even for HW interrupts, don't evaluate the HW state as
> + * all the guest is interested in is the virtual state.
> + */
> if (irq->active)
> value |= (1U << i);
>
> @@ -368,6 +403,29 @@ unsigned long vgic_mmio_read_active(struct kvm_vcpu *vcpu,
> return value;
> }
>
> +unsigned long vgic_mmio_read_active(struct kvm_vcpu *vcpu,
> + gpa_t addr, unsigned int len)
> +{
> + u32 intid = VGIC_ADDR_TO_INTID(addr, 1);
> + u32 val;
> +
> + mutex_lock(&vcpu->kvm->lock);
> + vgic_access_active_prepare(vcpu, intid);
> +
> + val = __vgic_mmio_read_active(vcpu, addr, len);
> +
> + vgic_access_active_finish(vcpu, intid);
> + mutex_unlock(&vcpu->kvm->lock);
> +
> + return val;
> +}
> +
> +unsigned long vgic_uaccess_read_active(struct kvm_vcpu *vcpu,
> + gpa_t addr, unsigned int len)
> +{
> + return __vgic_mmio_read_active(vcpu, addr, len);
> +}
> +
> /* Must be called with irq->irq_lock held */
> static void vgic_hw_irq_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
> bool active, bool is_uaccess)
> @@ -426,36 +484,6 @@ static void vgic_mmio_change_active(struct kvm_vcpu *vcpu, struct vgic_irq *irq,
> raw_spin_unlock_irqrestore(&irq->irq_lock, flags);
> }
>
> -/*
> - * If we are fiddling with an IRQ's active state, we have to make sure the IRQ
> - * is not queued on some running VCPU's LRs, because then the change to the
> - * active state can be overwritten when the VCPU's state is synced coming back
> - * from the guest.
> - *
> - * For shared interrupts, we have to stop all the VCPUs because interrupts can
> - * be migrated while we don't hold the IRQ locks and we don't want to be
> - * chasing moving targets.
> - *
> - * For private interrupts we don't have to do anything because userspace
> - * accesses to the VGIC state already require all VCPUs to be stopped, and
> - * only the VCPU itself can modify its private interrupts active state, which
> - * guarantees that the VCPU is not running.
> - */
> -static void vgic_change_active_prepare(struct kvm_vcpu *vcpu, u32 intid)
> -{
> - if (vcpu->kvm->arch.vgic.vgic_model == KVM_DEV_TYPE_ARM_VGIC_V3 ||
> - intid >= VGIC_NR_PRIVATE_IRQS)
> - kvm_arm_halt_guest(vcpu->kvm);
> -}
> -
> -/* See vgic_change_active_prepare */
> -static void vgic_change_active_finish(struct kvm_vcpu *vcpu, u32 intid)
> -{
> - if (vcpu->kvm->arch.vgic.vgic_model == KVM_DEV_TYPE_ARM_VGIC_V3 ||
> - intid >= VGIC_NR_PRIVATE_IRQS)
> - kvm_arm_resume_guest(vcpu->kvm);
> -}
> -
> static void __vgic_mmio_write_cactive(struct kvm_vcpu *vcpu,
> gpa_t addr, unsigned int len,
> unsigned long val)
> @@ -477,11 +505,11 @@ void vgic_mmio_write_cactive(struct kvm_vcpu *vcpu,
> u32 intid = VGIC_ADDR_TO_INTID(addr, 1);
>
> mutex_lock(&vcpu->kvm->lock);
> - vgic_change_active_prepare(vcpu, intid);
> + vgic_access_active_prepare(vcpu, intid);
>
> __vgic_mmio_write_cactive(vcpu, addr, len, val);
>
> - vgic_change_active_finish(vcpu, intid);
> + vgic_access_active_finish(vcpu, intid);
> mutex_unlock(&vcpu->kvm->lock);
> }
>
> @@ -514,11 +542,11 @@ void vgic_mmio_write_sactive(struct kvm_vcpu *vcpu,
> u32 intid = VGIC_ADDR_TO_INTID(addr, 1);
>
> mutex_lock(&vcpu->kvm->lock);
> - vgic_change_active_prepare(vcpu, intid);
> + vgic_access_active_prepare(vcpu, intid);
>
> __vgic_mmio_write_sactive(vcpu, addr, len, val);
>
> - vgic_change_active_finish(vcpu, intid);
> + vgic_access_active_finish(vcpu, intid);
> mutex_unlock(&vcpu->kvm->lock);
> }
>
> diff --git a/virt/kvm/arm/vgic/vgic-mmio.h b/virt/kvm/arm/vgic/vgic-mmio.h
> index 5af2aefad435..30713a44e3fa 100644
> --- a/virt/kvm/arm/vgic/vgic-mmio.h
> +++ b/virt/kvm/arm/vgic/vgic-mmio.h
> @@ -152,6 +152,9 @@ void vgic_mmio_write_cpending(struct kvm_vcpu *vcpu,
> unsigned long vgic_mmio_read_active(struct kvm_vcpu *vcpu,
> gpa_t addr, unsigned int len);
>
> +unsigned long vgic_uaccess_read_active(struct kvm_vcpu *vcpu,
> + gpa_t addr, unsigned int len);
> +
> void vgic_mmio_write_cactive(struct kvm_vcpu *vcpu,
> gpa_t addr, unsigned int len,
> unsigned long val);
>
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