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/vmx.c b/arch/x86/kvm/vmx.c
index 9b56032..cbca46a 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2249,6 +2249,20 @@
return 1;
}
+static int handle_task_switch(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
+{
+ unsigned long exit_qualification;
+ u16 tss_selector;
+ int reason;
+
+ exit_qualification = vmcs_readl(EXIT_QUALIFICATION);
+
+ reason = (u32)exit_qualification >> 30;
+ tss_selector = exit_qualification;
+
+ return kvm_task_switch(vcpu, tss_selector, reason);
+}
+
/*
* The exit handlers return 1 if the exit was handled fully and guest execution
* may resume. Otherwise they set the kvm_run parameter to indicate what needs
@@ -2271,6 +2285,7 @@
[EXIT_REASON_TPR_BELOW_THRESHOLD] = handle_tpr_below_threshold,
[EXIT_REASON_APIC_ACCESS] = handle_apic_access,
[EXIT_REASON_WBINVD] = handle_wbinvd,
+ [EXIT_REASON_TASK_SWITCH] = handle_task_switch,
};
static const int kvm_vmx_max_exit_handlers =