Commit 04cd8f86 authored by Sean Christopherson's avatar Sean Christopherson
Browse files

KVM: x86: Disallow KVM_CAP_X86_DISABLE_EXITS after vCPU creation 

Reject KVM_CAP_X86_DISABLE_EXITS if vCPUs have been created, as disabling
PAUSE/MWAIT/HLT exits after vCPUs have been created is broken and useless,
e.g. except for PAUSE on SVM, the relevant intercepts aren't updated after
vCPU creation.  vCPUs may also end up with an inconsistent configuration
if exits are disabled between creation of multiple vCPUs.

Cc: Hou Wenlong <houwenlong.hwl@antgroup.com>
Link: https://lore.kernel.org/all/9227068821b275ac547eb2ede09ec65d2281fe07.1680179693.git.houwenlong.hwl@antgroup.com
Link: https://lore.kernel.org/all/20230121020738.2973-2-kechenl@nvidia.com


Reviewed-by: default avatarMaxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: default avatarXiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: default avatarBinbin Wu <binbin.wu@linux.intel.com>
Link: https://lore.kernel.org/r/20241128013424.4096668-14-seanjc@google.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent 21d7f06d

Documentation/virt/kvm/api.rst

+1 −0
Original line number Diff line number Diff line
@@ -7670,6 +7670,7 @@ 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 vCPUs have already been created



Valid bits in args[0] are::

arch/x86/kvm/x86.c

+6 −0
Original line number Diff line number Diff line
@@ -6531,6 +6531,10 @@ 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_PAUSE)

			kvm->arch.pause_in_guest = true;
@@ -6552,6 +6556,8 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm, 
		}



		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];