KVM: selftests: Add helpers to make Xen-style VMCALL/VMMCALL hypercalls

Add wrappers to do hypercalls using VMCALL/VMMCALL and Xen's register ABI
(as opposed to full Xen-style hypercalls through a hypervisor provided
page).  Using the common helpers dedups a pile of code, and uses the
native hypercall instruction when running on AMD.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20230204024151.1373296-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Author: sean-jc

tools/testing/selftests/kvm/include/x86_64/processor.h

@@ -1063,6 +1063,8 @@ uint64_t *vm_get_page_table_entry(struct kvm_vm *vm, uint64_t vaddr);
 
 uint64_t kvm_hypercall(uint64_t nr, uint64_t a0, uint64_t a1, uint64_t a2,
 		       uint64_t a3);
+uint64_t __xen_hypercall(uint64_t nr, uint64_t a0, void *a1);
+void xen_hypercall(uint64_t nr, uint64_t a0, void *a1);
 
 void __vm_xsave_require_permission(int bit, const char *name);
 

tools/testing/selftests/kvm/lib/x86_64/processor.c

@@ -1161,6 +1161,16 @@ uint64_t kvm_hypercall(uint64_t nr, uint64_t a0, uint64_t a1, uint64_t a2,
 	return X86_HYPERCALL("a"(nr), "b"(a0), "c"(a1), "d"(a2), "S"(a3));
 }
 
+uint64_t __xen_hypercall(uint64_t nr, uint64_t a0, void *a1)
+{
+	return X86_HYPERCALL("a"(nr), "D"(a0), "S"(a1));
+}
+
+void xen_hypercall(uint64_t nr, uint64_t a0, void *a1)
+{
+	GUEST_ASSERT(!__xen_hypercall(nr, a0, a1));
+}
+
 const struct kvm_cpuid2 *kvm_get_supported_hv_cpuid(void)
 {
 	static struct kvm_cpuid2 *cpuid;

tools/testing/selftests/kvm/x86_64/xen_shinfo_test.c

@@ -225,15 +225,8 @@ static void guest_code(void)
 
 	/* Our turn. Deliver event channel (to ourselves) with
 	 * EVTCHNOP_send hypercall. */
-	unsigned long rax;
 	struct evtchn_send s = { .port = 127 };
-	__asm__ __volatile__ ("vmcall" :
-			      "=a" (rax) :
-			      "a" (__HYPERVISOR_event_channel_op),
-			      "D" (EVTCHNOP_send),
-			      "S" (&s));
-
-	GUEST_ASSERT(rax == 0);
+	xen_hypercall(__HYPERVISOR_event_channel_op, EVTCHNOP_send, &s);
 
 	guest_wait_for_irq();
 
@@ -242,24 +235,15 @@ static void guest_code(void)
 	/* Deliver "outbound" event channel to an eventfd which
 	 * happens to be one of our own irqfds. */
 	s.port = 197;
-	__asm__ __volatile__ ("vmcall" :
-			      "=a" (rax) :
-			      "a" (__HYPERVISOR_event_channel_op),
-			      "D" (EVTCHNOP_send),
-			      "S" (&s));
-
-	GUEST_ASSERT(rax == 0);
+	xen_hypercall(__HYPERVISOR_event_channel_op, EVTCHNOP_send, &s);
 
 	guest_wait_for_irq();
 
 	GUEST_SYNC(13);
 
 	/* Set a timer 100ms in the future. */
-	__asm__ __volatile__ ("vmcall" :
-			      "=a" (rax) :
-			      "a" (__HYPERVISOR_set_timer_op),
-			      "D" (rs->state_entry_time + 100000000));
-	GUEST_ASSERT(rax == 0);
+	xen_hypercall(__HYPERVISOR_set_timer_op,
+		      rs->state_entry_time + 100000000, NULL);
 
 	GUEST_SYNC(14);
 
@@ -281,51 +265,27 @@ static void guest_code(void)
 		.timeout = 0,
 	};
 
-	__asm__ __volatile__ ("vmcall" :
-			      "=a" (rax) :
-			      "a" (__HYPERVISOR_sched_op),
-			      "D" (SCHEDOP_poll),
-			      "S" (&p));
-
-	GUEST_ASSERT(rax == 0);
+	xen_hypercall(__HYPERVISOR_sched_op, SCHEDOP_poll, &p);
 
 	GUEST_SYNC(17);
 
 	/* Poll for an unset port and wait for the timeout. */
 	p.timeout = 100000000;
-	__asm__ __volatile__ ("vmcall" :
-			      "=a" (rax) :
-			      "a" (__HYPERVISOR_sched_op),
-			      "D" (SCHEDOP_poll),
-			      "S" (&p));
-
-	GUEST_ASSERT(rax == 0);
+	xen_hypercall(__HYPERVISOR_sched_op, SCHEDOP_poll, &p);
 
 	GUEST_SYNC(18);
 
 	/* A timer will wake the masked port we're waiting on, while we poll */
 	p.timeout = 0;
-	__asm__ __volatile__ ("vmcall" :
-			      "=a" (rax) :
-			      "a" (__HYPERVISOR_sched_op),
-			      "D" (SCHEDOP_poll),
-			      "S" (&p));
-
-	GUEST_ASSERT(rax == 0);
+	xen_hypercall(__HYPERVISOR_sched_op, SCHEDOP_poll, &p);
 
 	GUEST_SYNC(19);
 
 	/* A timer wake an *unmasked* port which should wake us with an
 	 * actual interrupt, while we're polling on a different port. */
 	ports[0]++;
 	p.timeout = 0;
-	__asm__ __volatile__ ("vmcall" :
-			      "=a" (rax) :
-			      "a" (__HYPERVISOR_sched_op),
-			      "D" (SCHEDOP_poll),
-			      "S" (&p));
-
-	GUEST_ASSERT(rax == 0);
+	xen_hypercall(__HYPERVISOR_sched_op, SCHEDOP_poll, &p);
 
 	guest_wait_for_irq();
 
@@ -360,12 +320,7 @@ static void guest_code(void)
 	 * timer IRQ is dropped due to an invalid event channel.
 	 */
 	for (i = 0; i < 100 && !guest_saw_irq; i++)
-		asm volatile("vmcall"
-			     : "=a" (rax)
-			     : "a" (__HYPERVISOR_sched_op),
-			       "D" (SCHEDOP_poll),
-			       "S" (&p)
-			     : "memory");
+		__xen_hypercall(__HYPERVISOR_sched_op, SCHEDOP_poll, &p);
 
 	/*
 	 * Re-send the timer IRQ if it was (likely) dropped due to the timer