[PATCH v4 12/13] KVM: selftests / xen: don't explicitly set the vcpu_info address

[Paul Durrant <paul@xen.org>]

From: Paul Durrant <pdurrant@amazon.com>

If the vCPU id is set and the shared_info is mapped using HVA then we can
infer that KVM has the ability to use a default vcpu_info mapping. Hence
we can stop setting the address of the vcpu_info structure.

NOTE: We still explicitly set vcpu_info half way through testing (to point
      at exactly the place it already is) to make sure that setting the
      attribute does not fail.

Signed-off-by: Paul Durrant <pdurrant@amazon.com>
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
---
Cc: Sean Christopherson <seanjc@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: David Woodhouse <dwmw2@infradead.org>

v3:
 - Add a guest sync point to set the vcpu_info attribute

v2:
 - New in this version.
---
 .../testing/selftests/kvm/x86_64/xen_shinfo_test.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

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 e786fa370140..7e74b3063437 100644
--- a/tools/testing/selftests/kvm/x86_64/xen_shinfo_test.c
+++ b/tools/testing/selftests/kvm/x86_64/xen_shinfo_test.c
@@ -68,6 +68,7 @@ enum {
 	TEST_POLL_TIMEOUT,
 	TEST_POLL_MASKED,
 	TEST_POLL_WAKE,
+	SET_VCPU_INFO,
 	TEST_TIMER_PAST,
 	TEST_LOCKING_SEND_RACE,
 	TEST_LOCKING_POLL_RACE,
@@ -327,6 +328,10 @@ static void guest_code(void)
 
 	GUEST_SYNC(TEST_POLL_WAKE);
 
+	/* Set the vcpu_info to point at exactly the place it already is to
+	 * make sure the attribute is functional. */
+	GUEST_SYNC(SET_VCPU_INFO);
+
 	/* A timer wake an *unmasked* port which should wake us with an
 	 * actual interrupt, while we're polling on a different port. */
 	ports[0]++;
@@ -549,7 +554,10 @@ int main(int argc, char *argv[])
 		.type = KVM_XEN_VCPU_ATTR_TYPE_VCPU_INFO,
 		.u.gpa = VCPU_INFO_ADDR,
 	};
-	vcpu_ioctl(vcpu, KVM_XEN_VCPU_SET_ATTR, &vi);
+
+	if (!has_vcpu_id || !has_shinfo_hva) {
+		vcpu_ioctl(vcpu, KVM_XEN_VCPU_SET_ATTR, &vi);
+	}
 
 	struct kvm_xen_vcpu_attr pvclock = {
 		.type = KVM_XEN_VCPU_ATTR_TYPE_VCPU_TIME_INFO,
@@ -903,6 +911,10 @@ int main(int argc, char *argv[])
 				alarm(1);
 				break;
 
+			case SET_VCPU_INFO:
+				vcpu_ioctl(vcpu, KVM_XEN_VCPU_SET_ATTR, &vi);
+				break;
+
 			case TEST_TIMER_PAST:
 				TEST_ASSERT(!evtchn_irq_expected,
 					    "Expected event channel IRQ but it didn't happen");
-- 
2.39.2