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Subject[PATCH 3/3] KVM: selftests: Add EVTCHNOP_send slow path test to xen_shinfo_test
Date
From: David Woodhouse <dwmw@amazon.co.uk>

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>
---
.../selftests/kvm/x86_64/xen_shinfo_test.c | 31 +++++++++++++++++++
1 file changed, 31 insertions(+)

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 644d614a9965..3adc2e11b094 100644
--- 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
@@ -801,6 +819,19 @@ 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");
--
2.35.3
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