KVM: VMX: Clean up DR6 emulation

As we trap all debug register accesses, we do not need to switch real
DR6 at all. Clean up update_exception_bitmap at this chance, too.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index c7b99e1..b7e812e 100644 (file)
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -579,17 +579,12 @@ static void update_exception_bitmap(struct kvm_vcpu *vcpu)
 {
        u32 eb;
 
-       eb = (1u << PF_VECTOR) | (1u << UD_VECTOR) | (1u << MC_VECTOR)
-               | (1u << NM_VECTOR);
-       /*
-        * Unconditionally intercept #DB so we can maintain dr6 without
-        * reading it every exit.
-        */
-       eb |= 1u << DB_VECTOR;
-       if (vcpu->guest_debug & KVM_GUESTDBG_ENABLE) {
-               if (vcpu->guest_debug & KVM_GUESTDBG_USE_SW_BP)
-                       eb |= 1u << BP_VECTOR;
-       }
+       eb = (1u << PF_VECTOR) | (1u << UD_VECTOR) | (1u << MC_VECTOR) |
+            (1u << NM_VECTOR) | (1u << DB_VECTOR);
+       if ((vcpu->guest_debug &
+            (KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_SW_BP)) ==
+           (KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_SW_BP))
+               eb |= 1u << BP_VECTOR;
        if (to_vmx(vcpu)->rmode.vm86_active)
                eb = ~0;
        if (enable_ept)
@@ -3777,9 +3772,6 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu)
         */
        vmcs_writel(HOST_CR0, read_cr0());
 
-       if (vcpu->arch.switch_db_regs)
-               set_debugreg(vcpu->arch.dr6, 6);
-
        asm(
                /* Store host registers */
                "push %%"R"dx; push %%"R"bp;"
@@ -3880,9 +3872,6 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu)
                                  | (1 << VCPU_EXREG_PDPTR));
        vcpu->arch.regs_dirty = 0;
 
-       if (vcpu->arch.switch_db_regs)
-               get_debugreg(vcpu->arch.dr6, 6);
-
        vmx->idt_vectoring_info = vmcs_read32(IDT_VECTORING_INFO_FIELD);
        if (vmx->rmode.irq.pending)
                fixup_rmode_irq(vmx);