Hi Vitaly,
On 2021-11-11 16:27, Vitaly Kuznetsov wrote:
It doesn't make sense to return the recommended maximum number of
vCPUs which exceeds the maximum possible number of vCPUs.
Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
---
arch/arm64/kvm/arm.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 7838e9fb693e..391dc7a921d5 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -223,7 +223,12 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm,
long ext)
r = 1;
break;
case KVM_CAP_NR_VCPUS:
- r = num_online_cpus();
+ if (kvm)
+ r = min_t(unsigned int, num_online_cpus(),
+ kvm->arch.max_vcpus);
+ else
+ r = min_t(unsigned int, num_online_cpus(),
+ kvm_arm_default_max_vcpus());
break;
case KVM_CAP_MAX_VCPUS:
case KVM_CAP_MAX_VCPU_ID:
This looks odd. This means that depending on the phase userspace is
in while initialising the VM, KVM_CAP_NR_VCPUS can return one thing
or the other.
For example, I create a VM on a 32 CPU system, NR_VCPUS says 32.
I create a GICv2 interrupt controller, it now says 8.
That's a change in behaviour that is visible by userspace, which
I'm keen on avoiding. I'd rather have the kvm and !kvm cases
return the same thing.
Thanks,
M.
--
Jazz is not dead. It just smells funny...
