KVM: VMX: pass correct DR6 for GD userspace exit

When KVM_EXIT_DEBUG is raised for the disabled-breakpoints case (DR7.GD),
DR6 was incorrectly copied from the value in the VM.  Instead,
DR6.BD should be set in order to catch this case.

On AMD this does not need any special code because the processor triggers
a #DB exception that is intercepted.  However, the testcase would fail
without the previous patch because both DR6.BS and DR6.BD would be set.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index e2b71b0cdfcef57146c4da5fe0ac6b51acd11af4..e45cf89c582191b6594df604ddfaece47f01d959 100644 (file)
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -4927,7 +4927,7 @@ static int handle_dr(struct kvm_vcpu *vcpu)
                 * guest debugging itself.
                 */
                if (vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP) {
-                       vcpu->run->debug.arch.dr6 = vcpu->arch.dr6;
+                       vcpu->run->debug.arch.dr6 = DR6_BD | DR6_RTM | DR6_FIXED_1;
                        vcpu->run->debug.arch.dr7 = dr7;
                        vcpu->run->debug.arch.pc = kvm_get_linear_rip(vcpu);
                        vcpu->run->debug.arch.exception = DB_VECTOR;

diff --git a/tools/testing/selftests/kvm/x86_64/debug_regs.c b/tools/testing/selftests/kvm/x86_64/debug_regs.c
index 077f25d61d1ac1d6f602b228cd29f36c721a67c2..8162c58a1234e87b1f761713f122c207adc6b91a 100644 (file)
--- a/tools/testing/selftests/kvm/x86_64/debug_regs.c
+++ b/tools/testing/selftests/kvm/x86_64/debug_regs.c
@@ -11,10 +11,13 @@
 
 #define VCPU_ID 0
 
+#define DR6_BD         (1 << 13)
+#define DR7_GD         (1 << 13)
+
 /* For testing data access debug BP */
 uint32_t guest_value;
 
-extern unsigned char sw_bp, hw_bp, write_data, ss_start;
+extern unsigned char sw_bp, hw_bp, write_data, ss_start, bd_start;
 
 static void guest_code(void)
 {
@@ -43,6 +46,8 @@ static void guest_code(void)
                     "rdmsr\n\t"
                     : : : "rax", "ecx");
 
+       /* DR6.BD test */
+       asm volatile("bd_start: mov %%dr0, %%rax" : : : "rax");
        GUEST_DONE();
 }
 
@@ -165,6 +170,23 @@ int main(void)
                            target_dr6);
        }
 
+       /* Finally test global disable */
+       CLEAR_DEBUG();
+       debug.control = KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_HW_BP;
+       debug.arch.debugreg[7] = 0x400 | DR7_GD;
+       APPLY_DEBUG();
+       vcpu_run(vm, VCPU_ID);
+       target_dr6 = 0xffff0ff0 | DR6_BD;
+       TEST_ASSERT(run->exit_reason == KVM_EXIT_DEBUG &&
+                   run->debug.arch.exception == DB_VECTOR &&
+                   run->debug.arch.pc == CAST_TO_RIP(bd_start) &&
+                   run->debug.arch.dr6 == target_dr6,
+                           "DR7.GD: exit %d exception %d rip 0x%llx "
+                           "(should be 0x%llx) dr6 0x%llx (should be 0x%llx)",
+                           run->exit_reason, run->debug.arch.exception,
+                           run->debug.arch.pc, target_rip, run->debug.arch.dr6,
+                           target_dr6);
+
        /* Disable all debug controls, run to the end */
        CLEAR_DEBUG();
        APPLY_DEBUG();