Commit 6440e5967bc broke old userspaces that do not set tss address
before entering vcpu. Unbreak it by setting tss address to a safe
value on the first vcpu entry. New userspaces should set tss address,
so print warning in case it doesn't.
Signed-off-by: Gleb Natapov <gleb@xxxxxxxxxx>
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index e2b8c6b..280b6ea 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -180,6 +180,7 @@ static u64 construct_eptp(unsigned long root_hpa);
static void kvm_cpu_vmxon(u64 addr);
static void kvm_cpu_vmxoff(void);
static void vmx_set_cr3(struct kvm_vcpu *vcpu, unsigned long cr3);
+static int vmx_set_tss_addr(struct kvm *kvm, unsigned int addr);
static DEFINE_PER_CPU(struct vmcs *, vmxarea);
static DEFINE_PER_CPU(struct vmcs *, current_vmcs);
@@ -1762,6 +1763,16 @@ static void enter_rmode(struct kvm_vcpu *vcpu)
vmx->emulation_required = 1;
vmx->rmode.vm86_active = 1;
+ /*
+ * Very old userspace does not call KVM_SET_TSS_ADDR before entering
+ * vcpu. Call it here with phys address pointing 16M below 4G.
+ */
+ if (!vcpu->kvm->arch.tss_addr) {
+ printk_once(KERN_WARNING "kvm: KVM_SET_TSS_ADDR need to be "
+ "called before entering vcpu\n");
+ vmx_set_tss_addr(vcpu->kvm, 0xfeffd000);
+ }
+
vmx->rmode.tr.selector = vmcs_read16(GUEST_TR_SELECTOR);
vmx->rmode.tr.base = vmcs_readl(GUEST_TR_BASE);
vmcs_writel(GUEST_TR_BASE, rmode_tss_base(vcpu->kvm));
--
Gleb.
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