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

Auger Eric
2017-05-16T12:39:18Z

Hi Jean, Christoffer,

On 16/05/2017 13:23, Jean-Philippe Brucker wrote:
> 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();

in QEMU use case, kvm_vgic_vcpu_init/vgic_register_redist_iodev does
nothing since KVM_VGIC_V3_ADDR_TYPE_REDIST was not called yet and
vgic->vgic_redist_base is undefined. Thus we postpone the redist_iodev
registration until the redist base address is set.

In QEMU case KVM_VGIC_V3_ADDR_TYPE_REDIST is called when all the CPUs
are initialized and we were lucky.
>
> ... 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.

changing the proto of kvm_arch_vcpu_postcreate and moving the
kvm_vgic_vcpu_init there could be an alternative.
By the way kvm_arch_vcpu_postcreate calls kvm_vgic_early_init() which
looks strange now that we do something clever before.

Thoughts?

Thanks

Eric
>
> 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);
>>
>
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