From fff9f5558d0e0813d4f80bfe1602acf225eca4fd Mon Sep 17 00:00:00 2001 From: Eric Auger Date: Thu, 3 Oct 2019 17:46:40 +0200 Subject: [PATCH] ARM: KVM: Check KVM_CAP_ARM_IRQ_LINE_LAYOUT_2 for smp_cpus > 256 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 within any ARM kvm accelerated machine. Signed-off-by: Eric Auger Reviewed-by: Richard Henderson Reviewed-by: Andrew Jones Acked-by: Marc Zyngier Message-id: 20191003154640.22451-4-eric.auger@redhat.com Signed-off-by: Peter Maydell --- target/arm/kvm.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/target/arm/kvm.c b/target/arm/kvm.c index b10581fa06..b473c63edb 100644 --- a/target/arm/kvm.c +++ b/target/arm/kvm.c @@ -182,6 +182,7 @@ int kvm_arm_get_max_vm_ipa_size(MachineState *ms) int kvm_arch_init(MachineState *ms, KVMState *s) { + int ret = 0; /* For ARM interrupt delivery is always asynchronous, * whether we are using an in-kernel VGIC or not. */ @@ -195,7 +196,14 @@ int kvm_arch_init(MachineState *ms, KVMState *s) cap_has_mp_state = kvm_check_extension(s, KVM_CAP_MP_STATE); - return 0; + if (ms->smp.cpus > 256 && + !kvm_check_extension(s, KVM_CAP_ARM_IRQ_LINE_LAYOUT_2)) { + error_report("Using more than 256 vcpus requires a host kernel " + "with KVM_CAP_ARM_IRQ_LINE_LAYOUT_2"); + ret = -EINVAL; + } + + return ret; } unsigned long kvm_arch_vcpu_id(CPUState *cpu)