From: Sean Christopherson seanjc@google.com

Since VMX and SVM both would never update the control bits if exits are disable after vCPUs are created, only allow setting exits disable flag before vCPU creation.

Fixes: 4d5422cea3b6 ("KVM: X86: Provide a capability to disable MWAIT intercepts")

Signed-off-by: Sean Christopherson seanjc@google.com Signed-off-by: Kechen Lu kechenl@nvidia.com Cc: stable@vger.kernel.org --- Documentation/virt/kvm/api.rst | 1 + arch/x86/kvm/x86.c | 6 ++++++ 2 files changed, 7 insertions(+)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 9807b05a1b57..fb0fcc566d5a 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -7087,6 +7087,7 @@ branch to guests' 0x200 interrupt vector. :Architectures: x86 :Parameters: args[0] defines which exits are disabled :Returns: 0 on success, -EINVAL when args[0] contains invalid exits + or if any vCPU has already been created

Valid bits in args[0] are::

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index da4bbd043a7b..c8ae9c4f9f08 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -6227,6 +6227,10 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm, if (cap->args[0] & ~KVM_X86_DISABLE_VALID_EXITS) break;

+ mutex_lock(&kvm->lock); + if (kvm->created_vcpus) + goto disable_exits_unlock; + if ((cap->args[0] & KVM_X86_DISABLE_EXITS_MWAIT) && kvm_can_mwait_in_guest()) kvm->arch.mwait_in_guest = true; @@ -6237,6 +6241,8 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm, if (cap->args[0] & KVM_X86_DISABLE_EXITS_CSTATE) kvm->arch.cstate_in_guest = true; r = 0; +disable_exits_unlock: + mutex_unlock(&kvm->lock); break; case KVM_CAP_MSR_PLATFORM_INFO: kvm->arch.guest_can_read_msr_platform_info = cap->args[0];