On Wed, Sep 11, 2019 at 05:51:25PM +0200, Eric Auger wrote:
> Host kernel within [4.18, 5.3] report an erroneous KVM_MAX_VCPUS=512
> for ARM. The actual capability to instantiate more than 256 vcpus
> was fixed in 5.4 with the upgrade of the KVM_IRQ_LINE ABI to support
> vcpu id encoded on 12 bits instead of 8 and a redistributor consuming
> a single KVM IO device instead of 2.
>
> So let's check this capability when attempting to use more than 256
> vcpus.
>
> Signed-off-by: Eric Auger <eric.au...@redhat.com>
> ---
> hw/arm/virt.c | 4 ++++
> target/arm/kvm.c | 21 +++++++++++++++++++++
> target/arm/kvm_arm.h | 15 +++++++++++++++
> 3 files changed, 40 insertions(+)
>
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index 0d1629ccb3..465e3140f7 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -1575,6 +1575,10 @@ static void machvirt_init(MachineState *machine)
> virt_max_cpus = GIC_NCPU;
> }
>
> + if (kvm_arm_irq_line_layout_mismatch(MACHINE(vms), max_cpus)) {
> + exit(1);
> + }
> +
> if (max_cpus > virt_max_cpus) {
> error_report("Number of SMP CPUs requested (%d) exceeds max CPUs "
> "supported by machine 'mach-virt' (%d)",
> diff --git a/target/arm/kvm.c b/target/arm/kvm.c
> index 6cdfa2204f..b601e2f35a 100644
> --- a/target/arm/kvm.c
> +++ b/target/arm/kvm.c
> @@ -171,6 +171,27 @@ bool kvm_arm_pmu_supported(CPUState *cpu)
> return kvm_check_extension(s, KVM_CAP_ARM_PMU_V3);
> }
>
> +bool kvm_arm_irq_line_layout_mismatch(MachineState *ms, int vcpus)
> +{
> + KVMState *s;
> + bool ret;
> +
> + if (!kvm_enabled()) {
> + return false;
> + }
> +
> + s = KVM_STATE(ms->accelerator);
> +
> + ret = vcpus > 256 &&
> + !kvm_check_extension(s, KVM_CAP_ARM_IRQ_LINE_LAYOUT_2);
> +
> + if (ret) {
> + error_report("Using more than 256 vcpus requires a host kernel "
> + "with KVM_CAP_ARM_IRQ_LINE_LAYOUT_2");
> + }
> + return ret;
> +}
> +
> int kvm_arm_get_max_vm_ipa_size(MachineState *ms)
> {
> KVMState *s = KVM_STATE(ms->accelerator);
> diff --git a/target/arm/kvm_arm.h b/target/arm/kvm_arm.h
> index b4e19457a0..d893d950d8 100644
> --- a/target/arm/kvm_arm.h
> +++ b/target/arm/kvm_arm.h
> @@ -233,6 +233,16 @@ bool kvm_arm_pmu_supported(CPUState *cs);
> */
> int kvm_arm_get_max_vm_ipa_size(MachineState *ms);
>
> +/**
> + * kvm_arm_irq_line_layout_mismatch - Returns whether the number of vcpus
> + * exceeds the limit imposed by the legacy KVM_IRQ_LINE ARM layout
> + * (without the vcpu2_index field).
> + *
> + * @ms: Machine state handle
> + * @vcpus: number of vcpus
> + */
> +bool kvm_arm_irq_line_layout_mismatch(MachineState *ms, int vcpus);
> +
> /**
> * kvm_arm_sync_mpstate_to_kvm
> * @cpu: ARMCPU
> @@ -281,6 +291,11 @@ static inline int
> kvm_arm_get_max_vm_ipa_size(MachineState *ms)
> return -ENOENT;
> }
>
> +static inline bool kvm_arm_irq_line_layout_mismatch(MachineState *ms, int
> vcpus)
> +{
> + return false;
> +}
> +
> static inline int kvm_arm_vgic_probe(void)
> {
> return 0;
> --
> 2.20.1
>
>
Reviewed-by: Andrew Jones <drjo...@redhat.com>
