KVM: x86: hardware task switching support
This emulates the x86 hardware task switch mechanism in software, as it is
unsupported by either vmx or svm. It allows operating systems which use it,
like freedos, to run as kvm guests.
Signed-off-by: Izik Eidus <izike@qumranet.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index c1c1b97..ad27346 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1112,9 +1112,18 @@
static int task_switch_interception(struct vcpu_svm *svm,
struct kvm_run *kvm_run)
{
- pr_unimpl(&svm->vcpu, "%s: task switch is unsupported\n", __func__);
- kvm_run->exit_reason = KVM_EXIT_UNKNOWN;
- return 0;
+ u16 tss_selector;
+
+ tss_selector = (u16)svm->vmcb->control.exit_info_1;
+ if (svm->vmcb->control.exit_info_2 &
+ (1ULL << SVM_EXITINFOSHIFT_TS_REASON_IRET))
+ return kvm_task_switch(&svm->vcpu, tss_selector,
+ TASK_SWITCH_IRET);
+ if (svm->vmcb->control.exit_info_2 &
+ (1ULL << SVM_EXITINFOSHIFT_TS_REASON_JMP))
+ return kvm_task_switch(&svm->vcpu, tss_selector,
+ TASK_SWITCH_JMP);
+ return kvm_task_switch(&svm->vcpu, tss_selector, TASK_SWITCH_CALL);
}
static int cpuid_interception(struct vcpu_svm *svm, struct kvm_run *kvm_run)