On Thu, Aug 21, 2014 at 02:06:47PM +0100, Andre Przywara wrote:
> Currently the maximum number of vCPUs supported is a global value
> limited by the used GIC model. GICv3 will lift this limit, but we
> still need to observe it for guests using GICv2.
> So the maximum number of vCPUs is per-VM value, depending on the
> GIC model the guest uses.
> Store and check the value in struct kvm_arch, but keep it down to
> 8 for now.
>
> Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
> ---
> arch/arm/include/asm/kvm_host.h | 1 +
> arch/arm/kvm/arm.c | 6 ++++++
> arch/arm64/include/asm/kvm_host.h | 3 +++
> virt/kvm/arm/vgic-v2.c | 5 +++++
> virt/kvm/arm/vgic-v3.c | 6 ++++++
> 5 files changed, 21 insertions(+)
>
> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
> index cf99ad0..0638419 100644
> --- a/arch/arm/include/asm/kvm_host.h
> +++ b/arch/arm/include/asm/kvm_host.h
> @@ -67,6 +67,7 @@ struct kvm_arch {
>
> /* Interrupt controller */
> struct vgic_dist vgic;
> + int max_vcpus;
> };
>
> #define KVM_NR_MEM_OBJS 40
> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> index 157e1b6..190f05f 100644
> --- a/arch/arm/kvm/arm.c
> +++ b/arch/arm/kvm/arm.c
> @@ -142,6 +142,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
>
> /* Mark the initial VMID generation invalid */
> kvm->arch.vmid_gen = 0;
> + kvm->arch.max_vcpus = CONFIG_KVM_ARM_MAX_VCPUS;
>
> return ret;
> out_free_stage2_pgd:
> @@ -223,6 +224,11 @@ struct kvm_vcpu *kvm_arch_vcpu_create(struct kvm *kvm, unsigned int id)
> int err;
> struct kvm_vcpu *vcpu;
>
> + if (id >= kvm->arch.max_vcpus) {
> + err = -EINVAL;
> + goto out;
> + }
> +
> vcpu = kmem_cache_zalloc(kvm_vcpu_cache, GFP_KERNEL);
> if (!vcpu) {
> err = -ENOMEM;
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 017fbae..a325161 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -58,6 +58,9 @@ struct kvm_arch {
> /* VTTBR value associated with above pgd and vmid */
> u64 vttbr;
>
> + /* The maximum number of vCPUs depends on the used GIC model */
> + int max_vcpus;
> +
> /* Interrupt controller */
> struct vgic_dist vgic;
>
> diff --git a/virt/kvm/arm/vgic-v2.c b/virt/kvm/arm/vgic-v2.c
> index 90947c6..c7362ff 100644
> --- a/virt/kvm/arm/vgic-v2.c
> +++ b/virt/kvm/arm/vgic-v2.c
> @@ -177,11 +177,16 @@ static struct vgic_params vgic_v2_params;
> static bool vgic_v2_init_emul(struct kvm *kvm, int type)
> {
> struct vgic_vm_ops *vm_ops = &kvm->arch.vgic.vm_ops;
> + int nr_vcpus;
>
> switch (type) {
> case KVM_DEV_TYPE_ARM_VGIC_V2:
> + nr_vcpus = atomic_read(&kvm->online_vcpus);
> + if (nr_vcpus > 8)
> + return false;
> vm_ops->get_lr = vgic_v2_get_lr;
> vm_ops->set_lr = vgic_v2_set_lr;
> + kvm->arch.max_vcpus = 8;
> return true;
> }
>
> diff --git a/virt/kvm/arm/vgic-v3.c b/virt/kvm/arm/vgic-v3.c
> index a38339e..86e8b99 100644
> --- a/virt/kvm/arm/vgic-v3.c
> +++ b/virt/kvm/arm/vgic-v3.c
> @@ -171,11 +171,17 @@ static const struct vgic_ops vgic_v3_ops = {
> static bool vgic_v3_init_emul_compat(struct kvm *kvm, int type)
> {
> struct vgic_vm_ops *vm_ops = &kvm->arch.vgic.vm_ops;
> + int nr_vcpus;
>
> switch (type) {
> case KVM_DEV_TYPE_ARM_VGIC_V2:
> + nr_vcpus = atomic_read(&kvm->online_vcpus);
> + if (nr_vcpus > 8)
> + return false;
> +
I have a feeling we could be seeing this error a bit, could we dedicate
an error code for the purpose or print a ratelimited warning or
something?
> vm_ops->get_lr = vgic_v3_get_lr;
> vm_ops->set_lr = vgic_v3_set_lr;
> + kvm->arch.max_vcpus = 8;
> return true;
> }
> return false;
> --
> 1.7.9.5
>
Thanks,
-Christoffer
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