Re: [PATCH v2 07/11] KVM: arm/arm64: Register iodevs when setting redist base and creating VCPUs

Jean-Philippe Brucker
2017-05-16T11:17:05Z

Hi,

On 09/05/17 09:56, Christoffer Dall wrote:
> Instead of waiting with registering KVM iodevs until the first VCPU is
> run, we can actually create the iodevs when the redist base address is
> set. The only downside is that we must now also check if we need to do
> this for VCPUs which are created after creating the VGIC, because there
> is no enforced ordering between creating the VGIC (and setting its base
> addresses) and creating the VCPUs.

This triggers a BUG(), when the order is VGIC init, then VCPU init (which
is what kvmtool does).

Issuing KVM_CREATE_VCPU after VGIC intialization produces the following calls:

kvm_vm_ioctl_create_vcpu
kvm_arch_vcpu_create
kvm_vcpu_init
kvm_arch_vcpu_init
kvm_vgic_vcpu_init
vgic_register_redist_iodev
kvm_vcpu_get_idx
... no VCPU registered yet in kvm->vcpus :(
BUG();

... would later register vcpu:
kvm->vcpus[atomic_read(&kvm->online_vcpus)] = vcpu

My quick fix is to move kvm_vgic_vcpu_init into kvm_arch_vcpu_postcreate,
but it discards the return value of kvm_vgic_vcpu_init, so I don't know
how to do it properly.

Thanks,
Jean

> Signed-off-by: Christoffer Dall <cdall@linaro.org>
> Reviewed-by: Eric Auger <eric.auger@redhat.com>
> ---
> include/kvm/arm_vgic.h | 1 +
> virt/kvm/arm/arm.c | 2 +-
> virt/kvm/arm/vgic/vgic-init.c | 21 ++++++++++++++++++
> virt/kvm/arm/vgic/vgic-kvm-device.c | 7 +++++-
> virt/kvm/arm/vgic/vgic-mmio-v3.c | 43 +++++++++++++++++++++++++++++++++++--
> virt/kvm/arm/vgic/vgic-v3.c | 6 ------
> virt/kvm/arm/vgic/vgic.h | 3 ++-
> 7 files changed, 72 insertions(+), 11 deletions(-)
>
> diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
> index fabcc64..4ff65ef 100644
> --- a/include/kvm/arm_vgic.h
> +++ b/include/kvm/arm_vgic.h
> @@ -286,6 +286,7 @@ extern struct static_key_false vgic_v2_cpuif_trap;
>
> int kvm_vgic_addr(struct kvm *kvm, unsigned long type, u64 *addr, bool write);
> void kvm_vgic_early_init(struct kvm *kvm);
> +int kvm_vgic_vcpu_init(struct kvm_vcpu *vcpu);
> int kvm_vgic_create(struct kvm *kvm, u32 type);
> void kvm_vgic_destroy(struct kvm *kvm);
> void kvm_vgic_vcpu_early_init(struct kvm_vcpu *vcpu);
> diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
> index 7941699..9f6f522a4b 100644
> --- a/virt/kvm/arm/arm.c
> +++ b/virt/kvm/arm/arm.c
> @@ -335,7 +335,7 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
>
> kvm_arm_reset_debug_ptr(vcpu);
>
> - return 0;
> + return kvm_vgic_vcpu_init(vcpu);
> }
>
> void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
> diff --git a/virt/kvm/arm/vgic/vgic-init.c b/virt/kvm/arm/vgic/vgic-init.c
> index 0ea64a1..962bb57 100644
> --- a/virt/kvm/arm/vgic/vgic-init.c
> +++ b/virt/kvm/arm/vgic/vgic-init.c
> @@ -226,6 +226,27 @@ static int kvm_vgic_dist_init(struct kvm *kvm, unsigned int nr_spis)
> return 0;
> }
>
> +/**
> + * kvm_vgic_vcpu_init() - Register VCPU-specific KVM iodevs
> + * @vcpu: pointer to the VCPU being created and initialized
> + */
> +int kvm_vgic_vcpu_init(struct kvm_vcpu *vcpu)
> +{
> + int ret = 0;
> + struct vgic_dist *dist = &vcpu->kvm->arch.vgic;
> +
> + if (!irqchip_in_kernel(vcpu->kvm))
> + return 0;
> +
> + /*
> + * If we are creating a VCPU with a GICv3 we must also register the
> + * KVM io device for the redistributor that belongs to this VCPU.
> + */
> + if (dist->vgic_model == KVM_DEV_TYPE_ARM_VGIC_V3)
> + ret = vgic_register_redist_iodev(vcpu);
> + return ret;
> +}
> +
> static void kvm_vgic_vcpu_enable(struct kvm_vcpu *vcpu)
> {
> if (kvm_vgic_global_state.type == VGIC_V2)
> diff --git a/virt/kvm/arm/vgic/vgic-kvm-device.c b/virt/kvm/arm/vgic/vgic-kvm-device.c
> index 69ccfd5..10ae6f3 100644
> --- a/virt/kvm/arm/vgic/vgic-kvm-device.c
> +++ b/virt/kvm/arm/vgic/vgic-kvm-device.c
> @@ -86,8 +86,13 @@ int kvm_vgic_addr(struct kvm *kvm, unsigned long type, u64 *addr, bool write)
> break;
> case KVM_VGIC_V3_ADDR_TYPE_REDIST:
> r = vgic_check_type(kvm, KVM_DEV_TYPE_ARM_VGIC_V3);
> + if (r)
> + break;
> + if (write) {
> + r = vgic_v3_set_redist_base(kvm, *addr);
> + goto out;
> + }
> addr_ptr = &vgic->vgic_redist_base;
> - alignment = SZ_64K;
> break;
> default:
> r = -ENODEV;
> diff --git a/virt/kvm/arm/vgic/vgic-mmio-v3.c b/virt/kvm/arm/vgic/vgic-mmio-v3.c
> index 168269b..99da1a2 100644
> --- a/virt/kvm/arm/vgic/vgic-mmio-v3.c
> +++ b/virt/kvm/arm/vgic/vgic-mmio-v3.c
> @@ -565,7 +565,7 @@ unsigned int vgic_v3_init_dist_iodev(struct vgic_io_device *dev)
> *
> * Return 0 on success, -ERRNO otherwise.
> */
> -static int vgic_register_redist_iodev(struct kvm_vcpu *vcpu)
> +int vgic_register_redist_iodev(struct kvm_vcpu *vcpu)
> {
> struct kvm *kvm = vcpu->kvm;
> struct vgic_dist *vgic = &kvm->arch.vgic;
> @@ -574,6 +574,18 @@ static int vgic_register_redist_iodev(struct kvm_vcpu *vcpu)
> gpa_t rd_base, sgi_base;
> int ret;
>
> + /*
> + * We may be creating VCPUs before having set the base address for the
> + * redistributor region, in which case we will come back to this
> + * function for all VCPUs when the base address is set. Just return
> + * without doing any work for now.
> + */
> + if (IS_VGIC_ADDR_UNDEF(vgic->vgic_redist_base))
> + return 0;
> +
> + if (!vgic_v3_check_base(kvm))
> + return -EINVAL;
> +
> rd_base = vgic->vgic_redist_base + kvm_vcpu_get_idx(vcpu) * SZ_64K * 2;
> sgi_base = rd_base + SZ_64K;
>
> @@ -619,7 +631,7 @@ static void vgic_unregister_redist_iodev(struct kvm_vcpu *vcpu)
> kvm_io_bus_unregister_dev(vcpu->kvm, KVM_MMIO_BUS, &sgi_dev->dev);
> }
>
> -int vgic_register_redist_iodevs(struct kvm *kvm)
> +static int vgic_register_all_redist_iodevs(struct kvm *kvm)
> {
> struct kvm_vcpu *vcpu;
> int c, ret = 0;
> @@ -641,6 +653,33 @@ int vgic_register_redist_iodevs(struct kvm *kvm)
> return ret;
> }
>
> +int vgic_v3_set_redist_base(struct kvm *kvm, u64 addr)
> +{
> + struct vgic_dist *vgic = &kvm->arch.vgic;
> + int ret;
> +
> + /* vgic_check_ioaddr makes sure we don't do this twice */
> + ret = vgic_check_ioaddr(kvm, &vgic->vgic_redist_base, addr, SZ_64K);
> + if (ret)
> + return ret;
> +
> + vgic->vgic_redist_base = addr;
> + if (!vgic_v3_check_base(kvm)) {
> + vgic->vgic_redist_base = VGIC_ADDR_UNDEF;
> + return -EINVAL;
> + }
> +
> + /*
> + * Register iodevs for each existing VCPU. Adding more VCPUs
> + * afterwards will register the iodevs when needed.
> + */
> + ret = vgic_register_all_redist_iodevs(kvm);
> + if (ret)
> + return ret;
> +
> + return 0;
> +}
> +
> int vgic_v3_has_attr_regs(struct kvm_device *dev, struct kvm_device_attr *attr)
> {
> const struct vgic_register_region *region;
> diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c
> index 2d53d7a..bb35078 100644
> --- a/virt/kvm/arm/vgic/vgic-v3.c
> +++ b/virt/kvm/arm/vgic/vgic-v3.c
> @@ -397,12 +397,6 @@ int vgic_v3_map_resources(struct kvm *kvm)
> goto out;
> }
>
> - ret = vgic_register_redist_iodevs(kvm);
> - if (ret) {
> - kvm_err("Unable to register VGICv3 redist MMIO regions\n");
> - goto out;
> - }
> -
> if (vgic_has_its(kvm)) {
> ret = vgic_register_its_iodevs(kvm);
> if (ret) {
> diff --git a/virt/kvm/arm/vgic/vgic.h b/virt/kvm/arm/vgic/vgic.h
> index 89eb935..5f17eac 100644
> --- a/virt/kvm/arm/vgic/vgic.h
> +++ b/virt/kvm/arm/vgic/vgic.h
> @@ -174,7 +174,8 @@ int vgic_v3_probe(const struct gic_kvm_info *info);
> int vgic_v3_map_resources(struct kvm *kvm);
> int vgic_v3_lpi_sync_pending_status(struct kvm *kvm, struct vgic_irq *irq);
> int vgic_v3_save_pending_tables(struct kvm *kvm);
> -int vgic_register_redist_iodevs(struct kvm *kvm);
> +int vgic_v3_set_redist_base(struct kvm *kvm, u64 addr);
> +int vgic_register_redist_iodev(struct kvm_vcpu *vcpu);
> bool vgic_v3_check_base(struct kvm *kvm);
>
> void vgic_v3_load(struct kvm_vcpu *vcpu);
>