[PATCH 1/2] KVM: selftests: Implement ucall() for s390x

[Thomas Huth <thuth@xxxxxxxxxx>]

On s390x, we can neither exit via PIO nor MMIO, but have to use
an instruction like DIAGNOSE. While we're at it, rename UCALL_PIO
to UCALL_DEFAULT, since PIO only works on x86 anyway, and this
way we can re-use the "default" type for the DIAGNOSE exit on s390x.

Now that ucall() is implemented, we can use it in the sync_reg_test
on s390x, too.

Signed-off-by: Thomas Huth <thuth@xxxxxxxxxx>
---
 .../testing/selftests/kvm/include/kvm_util.h  |  2 +-
 tools/testing/selftests/kvm/lib/ucall.c       | 34 +++++++++++++++----
 .../selftests/kvm/s390x/sync_regs_test.c      |  6 ++--
 3 files changed, 32 insertions(+), 10 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
index e0e66b115ef2..c37aea2e33e5 100644
--- a/tools/testing/selftests/kvm/include/kvm_util.h
+++ b/tools/testing/selftests/kvm/include/kvm_util.h
@@ -167,7 +167,7 @@ int vm_create_device(struct kvm_vm *vm, struct kvm_create_device *cd);
 
 /* ucall implementation types */
 typedef enum {
-	UCALL_PIO,
+	UCALL_DEFAULT,
 	UCALL_MMIO,
 } ucall_type_t;
 
diff --git a/tools/testing/selftests/kvm/lib/ucall.c b/tools/testing/selftests/kvm/lib/ucall.c
index dd9a66700f96..55534dd014dc 100644
--- a/tools/testing/selftests/kvm/lib/ucall.c
+++ b/tools/testing/selftests/kvm/lib/ucall.c
@@ -30,7 +30,7 @@ void ucall_init(struct kvm_vm *vm, ucall_type_t type, void *arg)
 	ucall_type = type;
 	sync_global_to_guest(vm, ucall_type);
 
-	if (type == UCALL_PIO)
+	if (type == UCALL_DEFAULT)
 		return;
 
 	if (type == UCALL_MMIO) {
@@ -84,11 +84,18 @@ void ucall_uninit(struct kvm_vm *vm)
 	sync_global_to_guest(vm, ucall_exit_mmio_addr);
 }
 
-static void ucall_pio_exit(struct ucall *uc)
+static void ucall_default_exit(struct ucall *uc)
 {
-#ifdef __x86_64__
+#if defined(__x86_64__)
+	/* Exit via PIO */
 	asm volatile("in %[port], %%al"
 		: : [port] "d" (UCALL_PIO_PORT), "D" (uc) : "rax");
+#elif defined(__s390x__)
+	/* Exit via DIAGNOSE 0x501 (normally used for breakpoints) */
+	asm volatile ("diag 0,%0,0x501" : : "a"(uc) : "memory");
+#else
+	fprintf(stderr, "No default ucall available on this architecture.\n");
+	exit(1);
 #endif
 }
 
@@ -113,8 +120,8 @@ void ucall(uint64_t cmd, int nargs, ...)
 	va_end(va);
 
 	switch (ucall_type) {
-	case UCALL_PIO:
-		ucall_pio_exit(&uc);
+	case UCALL_DEFAULT:
+		ucall_default_exit(&uc);
 		break;
 	case UCALL_MMIO:
 		ucall_mmio_exit(&uc);
@@ -128,15 +135,28 @@ uint64_t get_ucall(struct kvm_vm *vm, uint32_t vcpu_id, struct ucall *uc)
 	struct ucall ucall = {};
 	bool got_ucall = false;
 
-#ifdef __x86_64__
-	if (ucall_type == UCALL_PIO && run->exit_reason == KVM_EXIT_IO &&
+#if defined(__x86_64__)
+	if (ucall_type == UCALL_DEFAULT && run->exit_reason == KVM_EXIT_IO &&
 	    run->io.port == UCALL_PIO_PORT) {
 		struct kvm_regs regs;
 		vcpu_regs_get(vm, vcpu_id, &regs);
 		memcpy(&ucall, addr_gva2hva(vm, (vm_vaddr_t)regs.rdi), sizeof(ucall));
 		got_ucall = true;
 	}
+#elif defined(__s390x__)
+	if (ucall_type == UCALL_DEFAULT &&
+	    run->exit_reason == KVM_EXIT_S390_SIEIC &&
+	    run->s390_sieic.icptcode == 4 &&
+	    (run->s390_sieic.ipa >> 8) == 0x83 &&    /* 0x83 means DIAGNOSE */
+	    (run->s390_sieic.ipb >> 16) == 0x501) {
+		int reg = run->s390_sieic.ipa & 0xf;
+
+		memcpy(&ucall, addr_gva2hva(vm, run->s.regs.gprs[reg]),
+		       sizeof(ucall));
+		got_ucall = true;
+	}
 #endif
+
 	if (ucall_type == UCALL_MMIO && run->exit_reason == KVM_EXIT_MMIO &&
 	    run->mmio.phys_addr == (uint64_t)ucall_exit_mmio_addr) {
 		vm_vaddr_t gva;
diff --git a/tools/testing/selftests/kvm/s390x/sync_regs_test.c b/tools/testing/selftests/kvm/s390x/sync_regs_test.c
index e85ff0d69548..bbc93094519b 100644
--- a/tools/testing/selftests/kvm/s390x/sync_regs_test.c
+++ b/tools/testing/selftests/kvm/s390x/sync_regs_test.c
@@ -25,9 +25,11 @@
 
 static void guest_code(void)
 {
+	register u64 stage asm("11") = 0;
+
 	for (;;) {
-		asm volatile ("diag 0,0,0x501");
-		asm volatile ("ahi 11,1");
+		GUEST_SYNC(0);
+		asm volatile ("ahi %0,1" : : "r"(stage));
 	}
 }
 
-- 
2.21.0