On Thu, Mar 30, 2023, Hou Wenlong wrote: > Disable PAUSE/MWAIT/HLT exits after vCPUs have been created is useless, > because PAUSE/MWAIT/HLT intercepts configuration is not changed after > vCPU created. And two vCPUs may have inconsistent configuration if > disable PAUSE/MWAIT/HLT exits between those two vCPUs creation. Since > it's a per-VM capability, all vCPUs should keep same configuration, so > disallow enable KVM_CAP_X86_DISABLE_EXITS capability after vCPUs have > been created. > > Signed-off-by: Hou Wenlong <houwenlong.hwl@xxxxxxxxxxxx> > --- > Documentation/virt/kvm/api.rst | 3 ++- > arch/x86/kvm/x86.c | 5 +++++ > 2 files changed, 7 insertions(+), 1 deletion(-) > > diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst > index a69e91088d76..95a683a27cf2 100644 > --- a/Documentation/virt/kvm/api.rst > +++ b/Documentation/virt/kvm/api.rst > @@ -7179,7 +7179,8 @@ 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 > +:Returns: 0 on success, -EINVAL when args[0] contains invalid exits or > + any vCPUs have been created. > > Valid bits in args[0] are:: > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 2c0ff40e5345..7e97595465fc 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -6275,6 +6275,9 @@ 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_PAUSE) > kvm->arch.pause_in_guest = true; > > @@ -6296,6 +6299,8 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm, > } > > r = 0; > +disable_exits_unlock: Hah! I thought this looked familiar[*] :-) [*] https://lkml.kernel.org/r/DM6PR12MB35000D46146BA68EE294953BCACB9%40DM6PR12MB3500.namprd12.prod.outlook.com
