[PATCH v10 020/108] KVM: Support KVM_CAP_MAX_VCPUS for KVM_ENABLE_CAP

isaku.yamahata
2022-10-30T06:25:20Z

From: Isaku Yamahata <isaku.yamahata@intel.com>

TDX attestation includes the maximum number of vcpu that the guest can
accommodate. For that, the maximum number of vcpu needs to be specified
instead of constant, KVM_MAX_VCPUS. Make KVM_ENABLE_CAP support
KVM_CAP_MAX_VCPUS.

Suggested-by: Sagi Shahar <sagis@google.com>
Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
---
virt/kvm/kvm_main.c | 21 +++++++++++++++++++++
1 file changed, 21 insertions(+)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index b9c270f97c88..3b05a3396f89 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -4967,6 +4967,27 @@ static int kvm_vm_ioctl_enable_cap_generic(struct kvm *kvm,
case KVM_CAP_DIRTY_LOG_RING:
case KVM_CAP_DIRTY_LOG_RING_ACQ_REL:
return kvm_vm_ioctl_enable_dirty_log_ring(kvm, cap->args[0]);
+ case KVM_CAP_MAX_VCPUS: {
+ int r;
+
+ if (cap->flags || cap->args[0] == 0)
+ return -EINVAL;
+ if (cap->args[0] > kvm_vm_ioctl_check_extension(kvm, KVM_CAP_MAX_VCPUS))
+ return -E2BIG;
+
+ mutex_lock(&kvm->lock);
+ /* Only decreasing is allowed. */
+ if (cap->args[0] > kvm->max_vcpus)
+ r = -E2BIG;
+ else if (kvm->created_vcpus)
+ r = -EBUSY;
+ else {
+ kvm->max_vcpus = cap->args[0];
+ r = 0;
+ }
+ mutex_unlock(&kvm->lock);
+ return r;
+ }
default:
return kvm_vm_ioctl_enable_cap(kvm, cap);
}
--
2.25.1