KVM: selftests: Add EVTCHNOP_send slow path test to xen_shinfo_test

When kvm_xen_evtchn_send() takes the slow path because the shinfo GPC
needs to be revalidated, it used to violate the SRCU vs. kvm->lock
locking rules and potentially cause a deadlock.

Now that lockdep is learning to catch such things, make sure that code
path is exercised by the selftest.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>

diff --git a/tools/testing/selftests/kvm/x86_64/xen_shinfo_test.c b/tools/testing/selftests/kvm/x86_64/xen_shinfo_test.c
index 60f892955283ea87de770f222fe61fd4852b4f0e..e9a6be3e825989f5f6abc1dc593814e455dd2f33 100644 (file)
--- a/tools/testing/selftests/kvm/x86_64/xen_shinfo_test.c
+++ b/tools/testing/selftests/kvm/x86_64/xen_shinfo_test.c
@@ -29,6 +29,9 @@
 #define DUMMY_REGION_GPA       (SHINFO_REGION_GPA + (3 * PAGE_SIZE))
 #define DUMMY_REGION_SLOT      11
 
+#define DUMMY_REGION_GPA_2     (SHINFO_REGION_GPA + (4 * PAGE_SIZE))
+#define DUMMY_REGION_SLOT_2    12
+
 #define SHINFO_ADDR    (SHINFO_REGION_GPA)
 #define VCPU_INFO_ADDR (SHINFO_REGION_GPA + 0x40)
 #define PVTIME_ADDR    (SHINFO_REGION_GPA + PAGE_SIZE)
@@ -57,6 +60,7 @@ enum {
        TEST_EVTCHN_SLOWPATH,
        TEST_EVTCHN_SEND_IOCTL,
        TEST_EVTCHN_HCALL,
+       TEST_EVTCHN_HCALL_SLOWPATH,
        TEST_EVTCHN_HCALL_EVENTFD,
        TEST_TIMER_SETUP,
        TEST_TIMER_WAIT,
@@ -270,6 +274,20 @@ static void guest_code(void)
 
        guest_wait_for_irq();
 
+       GUEST_SYNC(TEST_EVTCHN_HCALL_SLOWPATH);
+
+       /* Same again, but this time the host has messed with memslots
+        * so it should take the slow path in kvm_xen_set_evtchn(). */
+       __asm__ __volatile__ ("vmcall" :
+                             "=a" (rax) :
+                             "a" (__HYPERVISOR_event_channel_op),
+                             "D" (EVTCHNOP_send),
+                             "S" (&s));
+
+       GUEST_ASSERT(rax == 0);
+
+       guest_wait_for_irq();
+
        GUEST_SYNC(TEST_EVTCHN_HCALL_EVENTFD);
 
        /* Deliver "outbound" event channel to an eventfd which
@@ -800,6 +818,19 @@ int main(int argc, char *argv[])
                                alarm(1);
                                break;
 
+                       case TEST_EVTCHN_HCALL_SLOWPATH:
+                               TEST_ASSERT(!evtchn_irq_expected,
+                                           "Expected event channel IRQ but it didn't happen");
+                               shinfo->evtchn_pending[0] = 0;
+
+                               if (verbose)
+                                       printf("Testing guest EVTCHNOP_send direct to evtchn after memslot change\n");
+                               vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS,
+                                                           DUMMY_REGION_GPA_2, DUMMY_REGION_SLOT_2, 1, 0);
+                               evtchn_irq_expected = true;
+                               alarm(1);
+                               break;
+
                        case TEST_EVTCHN_HCALL_EVENTFD:
                                TEST_ASSERT(!evtchn_irq_expected,
                                            "Expected event channel IRQ but it didn't happen");