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 <eric.au...@redhat.com>
---
v2 -> v3:
- Implement the check in kvm_arch_init as suggested by Peter
---
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)
--
2.20.1
