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 <[email protected]> --- hw/arm/virt.c | 7 +++++++ target/arm/kvm.c | 7 +++++++ target/arm/kvm_arm.h | 13 +++++++++++++ 3 files changed, 27 insertions(+) diff --git a/hw/arm/virt.c b/hw/arm/virt.c index 0d1629ccb3..bcc8d64384 100644 --- a/hw/arm/virt.c +++ b/hw/arm/virt.c @@ -1575,6 +1575,13 @@ static void machvirt_init(MachineState *machine) virt_max_cpus = GIC_NCPU; } + if (kvm_enabled() && max_cpus > 256 && + !kvm_arm_irq_line_layout_2(MACHINE(vms))) { + error_report("Using more than 256 vcpus require a host kernel " + "with KVM_CAP_ARM_IRQ_LINE_LAYOUT_2"); + 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 b2eaa50b8d..db88fcc5bf 100644 --- a/target/arm/kvm.c +++ b/target/arm/kvm.c @@ -171,6 +171,13 @@ bool kvm_arm_pmu_supported(CPUState *cpu) return kvm_check_extension(s, KVM_CAP_ARM_PMU_V3); } +bool kvm_arm_irq_line_layout_2(MachineState *ms) +{ + KVMState *s = KVM_STATE(ms->accelerator); + + return kvm_check_extension(s, KVM_CAP_ARM_IRQ_LINE_LAYOUT_2); +} + 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 b3106c8600..06b4db4513 100644 --- a/target/arm/kvm_arm.h +++ b/target/arm/kvm_arm.h @@ -233,6 +233,14 @@ bool kvm_arm_pmu_supported(CPUState *cs); */ int kvm_arm_get_max_vm_ipa_size(MachineState *ms); +/** + * kvm_arm_irq_line_layout_2 - Returns whether more than 256 + * vcpus are supported by KVM_IRQ_LINE + * + * @ms: Machine state handle + */ +bool kvm_arm_irq_line_layout_2(MachineState *ms); + /** * kvm_arm_sync_mpstate_to_kvm * @cpu: ARMCPU @@ -280,6 +288,11 @@ static inline int kvm_arm_get_max_vm_ipa_size(MachineState *ms) return -ENOENT; } +static inline int kvm_arm_irq_line_layout_2(MachineState *ms) +{ + return -ENOENT; +} + static inline int kvm_arm_vgic_probe(void) { return 0; -- 2.20.1
