[kvm-unit-tests PATCH v2 3/5] s390x: Add library functions for exiting from snippet

[Nina Schoetterl-Glausch <nsg@linux.ibm.com>]

It is useful to be able to force an exit to the host from the snippet,
as well as do so while returning a value.
Add this functionality, also add helper functions for the host to check
for an exit and get or check the value.
Use diag 0x44 and 0x9c for this.
Add a guest specific snippet header file and rename snippet.h to reflect
that it is host specific.

Signed-off-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
---
 s390x/Makefile                          |  1 +
 lib/s390x/asm/arch_def.h                | 13 ++++++++
 lib/s390x/sie.h                         |  1 +
 lib/s390x/snippet-guest.h               | 26 +++++++++++++++
 lib/s390x/{snippet.h => snippet-host.h} | 10 ++++--
 lib/s390x/sie.c                         | 31 ++++++++++++++++++
 lib/s390x/snippet-host.c                | 42 +++++++++++++++++++++++++
 lib/s390x/uv.c                          |  2 +-
 s390x/mvpg-sie.c                        |  2 +-
 s390x/pv-diags.c                        |  2 +-
 s390x/pv-icptcode.c                     |  2 +-
 s390x/pv-ipl.c                          |  2 +-
 s390x/sie-dat.c                         |  2 +-
 s390x/spec_ex-sie.c                     |  2 +-
 s390x/uv-host.c                         |  2 +-
 15 files changed, 129 insertions(+), 11 deletions(-)
 create mode 100644 lib/s390x/snippet-guest.h
 rename lib/s390x/{snippet.h => snippet-host.h} (92%)
 create mode 100644 lib/s390x/snippet-host.c

diff --git a/s390x/Makefile b/s390x/Makefile
index f79fd009..a10695a2 100644
--- a/s390x/Makefile
+++ b/s390x/Makefile
@@ -109,6 +109,7 @@ cflatobjs += lib/s390x/css_lib.o
 cflatobjs += lib/s390x/malloc_io.o
 cflatobjs += lib/s390x/uv.o
 cflatobjs += lib/s390x/sie.o
+cflatobjs += lib/s390x/snippet-host.o
 cflatobjs += lib/s390x/fault.o
 
 OBJDIRS += lib/s390x
diff --git a/lib/s390x/asm/arch_def.h b/lib/s390x/asm/arch_def.h
index 745a3387..db04deca 100644
--- a/lib/s390x/asm/arch_def.h
+++ b/lib/s390x/asm/arch_def.h
@@ -504,4 +504,17 @@ static inline uint32_t get_prefix(void)
 	return current_prefix;
 }
 
+static inline void diag44(void)
+{
+	asm volatile("diag	0,0,0x44\n");
+}
+
+static inline void diag9c(uint64_t val)
+{
+	asm volatile("diag	%[val],0,0x9c\n"
+		:
+		: [val] "d"(val)
+	);
+}
+
 #endif
diff --git a/lib/s390x/sie.h b/lib/s390x/sie.h
index c1724cf2..18fdd72e 100644
--- a/lib/s390x/sie.h
+++ b/lib/s390x/sie.h
@@ -281,6 +281,7 @@ void sie_expect_validity(struct vm *vm);
 uint16_t sie_get_validity(struct vm *vm);
 void sie_check_validity(struct vm *vm, uint16_t vir_exp);
 void sie_handle_validity(struct vm *vm);
+bool sie_is_diag_icpt(struct vm *vm, unsigned int diag);
 void sie_guest_sca_create(struct vm *vm);
 void sie_guest_create(struct vm *vm, uint64_t guest_mem, uint64_t guest_mem_len);
 void sie_guest_destroy(struct vm *vm);
diff --git a/lib/s390x/snippet-guest.h b/lib/s390x/snippet-guest.h
new file mode 100644
index 00000000..e82e8e29
--- /dev/null
+++ b/lib/s390x/snippet-guest.h
@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Snippet functionality for the guest.
+ *
+ * Copyright IBM Corp. 2023
+ */
+
+#ifndef _S390X_SNIPPET_GUEST_H_
+#define _S390X_SNIPPET_GUEST_H_
+
+#include <asm/arch_def.h>
+#include <asm/barrier.h>
+
+static inline void force_exit(void)
+{
+	diag44();
+	mb(); /* allow host to modify guest memory */
+}
+
+static inline void force_exit_value(uint64_t val)
+{
+	diag9c(val);
+	mb(); /* allow host to modify guest memory */
+}
+
+#endif
diff --git a/lib/s390x/snippet.h b/lib/s390x/snippet-host.h
similarity index 92%
rename from lib/s390x/snippet.h
rename to lib/s390x/snippet-host.h
index 910849aa..230b25b0 100644
--- a/lib/s390x/snippet.h
+++ b/lib/s390x/snippet-host.h
@@ -1,13 +1,13 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
 /*
- * Snippet definitions
+ * Snippet functionality for the host.
  *
  * Copyright IBM Corp. 2021
  * Author: Janosch Frank <frankja@linux.ibm.com>
  */
 
-#ifndef _S390X_SNIPPET_H_
-#define _S390X_SNIPPET_H_
+#ifndef _S390X_SNIPPET_HOST_H_
+#define _S390X_SNIPPET_HOST_H_
 
 #include <sie.h>
 #include <uv.h>
@@ -144,4 +144,8 @@ static inline void snippet_setup_guest(struct vm *vm, bool is_pv)
 	}
 }
 
+bool snippet_is_force_exit(struct vm *vm);
+bool snippet_is_force_exit_value(struct vm *vm);
+uint64_t snippet_get_force_exit_value(struct vm *vm);
+void snippet_check_force_exit_value(struct vm *vm, uint64_t exit_exp);
 #endif
diff --git a/lib/s390x/sie.c b/lib/s390x/sie.c
index 40936bd2..6bda493d 100644
--- a/lib/s390x/sie.c
+++ b/lib/s390x/sie.c
@@ -42,6 +42,37 @@ void sie_check_validity(struct vm *vm, uint16_t vir_exp)
 	report(vir_exp == vir, "VALIDITY: %x", vir);
 }
 
+bool sie_is_diag_icpt(struct vm *vm, unsigned int diag)
+{
+	union {
+		struct {
+			uint64_t     : 16;
+			uint64_t ipa : 16;
+			uint64_t ipb : 32;
+		};
+		struct {
+			uint64_t          : 16;
+			uint64_t opcode   :  8;
+			uint64_t r_1      :  4;
+			uint64_t r_2      :  4;
+			uint64_t r_base   :  4;
+			uint64_t displace : 12;
+			uint64_t zero     : 16;
+		};
+	} instr = { .ipa = vm->sblk->ipa, .ipb = vm->sblk->ipb };
+	uint64_t code;
+
+	assert(diag == 0x44 || diag == 0x9c);
+
+	if (vm->sblk->icptcode != ICPT_INST)
+		return false;
+	if (instr.opcode != 0x83 || instr.zero)
+		return false;
+	code = instr.r_base ? vm->save_area.guest.grs[instr.r_base] : 0;
+	code = (code + instr.displace) & 0xffff;
+	return code == diag;
+}
+
 void sie_handle_validity(struct vm *vm)
 {
 	if (vm->sblk->icptcode != ICPT_VALIDITY)
diff --git a/lib/s390x/snippet-host.c b/lib/s390x/snippet-host.c
new file mode 100644
index 00000000..44a60bb9
--- /dev/null
+++ b/lib/s390x/snippet-host.c
@@ -0,0 +1,42 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Snippet functionality for the host.
+ *
+ * Copyright IBM Corp. 2023
+ */
+
+#include <libcflat.h>
+#include <snippet-host.h>
+#include <sie.h>
+
+bool snippet_is_force_exit(struct vm *vm)
+{
+	return sie_is_diag_icpt(vm, 0x44);
+}
+
+bool snippet_is_force_exit_value(struct vm *vm)
+{
+	return sie_is_diag_icpt(vm, 0x9c);
+}
+
+uint64_t snippet_get_force_exit_value(struct vm *vm)
+{
+	struct kvm_s390_sie_block *sblk = vm->sblk;
+
+	assert(snippet_is_force_exit_value(vm));
+
+	return vm->save_area.guest.grs[(sblk->ipa & 0xf0) >> 4];
+}
+
+void snippet_check_force_exit_value(struct vm *vm, uint64_t value_exp)
+{
+	uint64_t value;
+
+	if (snippet_is_force_exit_value(vm)) {
+		value = snippet_get_force_exit_value(vm);
+		report(value == value_exp, "guest forced exit with value (0x%lx == 0x%lx)",
+		       value, value_exp);
+	} else {
+		report_fail("guest forced exit with value");
+	}
+}
diff --git a/lib/s390x/uv.c b/lib/s390x/uv.c
index 23a86179..81e9a71e 100644
--- a/lib/s390x/uv.c
+++ b/lib/s390x/uv.c
@@ -18,7 +18,7 @@
 #include <asm/uv.h>
 #include <uv.h>
 #include <sie.h>
-#include <snippet.h>
+#include <snippet-host.h>
 
 static struct uv_cb_qui uvcb_qui = {
 	.header.cmd = UVC_CMD_QUI,
diff --git a/s390x/mvpg-sie.c b/s390x/mvpg-sie.c
index d182b49a..3aec9d71 100644
--- a/s390x/mvpg-sie.c
+++ b/s390x/mvpg-sie.c
@@ -19,7 +19,7 @@
 #include <alloc_page.h>
 #include <sclp.h>
 #include <sie.h>
-#include <snippet.h>
+#include <snippet-host.h>
 
 static struct vm vm;
 
diff --git a/s390x/pv-diags.c b/s390x/pv-diags.c
index 3193ad99..7fb7f091 100644
--- a/s390x/pv-diags.c
+++ b/s390x/pv-diags.c
@@ -8,7 +8,7 @@
  *  Janosch Frank <frankja@linux.ibm.com>
  */
 #include <libcflat.h>
-#include <snippet.h>
+#include <snippet-host.h>
 #include <pv_icptdata.h>
 #include <sie.h>
 #include <sclp.h>
diff --git a/s390x/pv-icptcode.c b/s390x/pv-icptcode.c
index d7c47d6f..9a9c7357 100644
--- a/s390x/pv-icptcode.c
+++ b/s390x/pv-icptcode.c
@@ -12,7 +12,7 @@
 #include <sie.h>
 #include <smp.h>
 #include <sclp.h>
-#include <snippet.h>
+#include <snippet-host.h>
 #include <pv_icptdata.h>
 #include <asm/facility.h>
 #include <asm/barrier.h>
diff --git a/s390x/pv-ipl.c b/s390x/pv-ipl.c
index cc46e7f7..7d654b84 100644
--- a/s390x/pv-ipl.c
+++ b/s390x/pv-ipl.c
@@ -10,7 +10,7 @@
 #include <libcflat.h>
 #include <sie.h>
 #include <sclp.h>
-#include <snippet.h>
+#include <snippet-host.h>
 #include <pv_icptdata.h>
 #include <asm/facility.h>
 #include <asm/uv.h>
diff --git a/s390x/sie-dat.c b/s390x/sie-dat.c
index f0257770..9e60f26e 100644
--- a/s390x/sie-dat.c
+++ b/s390x/sie-dat.c
@@ -16,7 +16,7 @@
 #include <alloc_page.h>
 #include <sclp.h>
 #include <sie.h>
-#include <snippet.h>
+#include <snippet-host.h>
 #include "snippets/c/sie-dat.h"
 
 static struct vm vm;
diff --git a/s390x/spec_ex-sie.c b/s390x/spec_ex-sie.c
index fe2f23ee..0ad7ec08 100644
--- a/s390x/spec_ex-sie.c
+++ b/s390x/spec_ex-sie.c
@@ -13,7 +13,7 @@
 #include <asm/arch_def.h>
 #include <alloc_page.h>
 #include <sie.h>
-#include <snippet.h>
+#include <snippet-host.h>
 #include <hardware.h>
 
 static struct vm vm;
diff --git a/s390x/uv-host.c b/s390x/uv-host.c
index 55b46446..87d108b6 100644
--- a/s390x/uv-host.c
+++ b/s390x/uv-host.c
@@ -15,7 +15,7 @@
 #include <sclp.h>
 #include <smp.h>
 #include <uv.h>
-#include <snippet.h>
+#include <snippet-host.h>
 #include <mmu.h>
 #include <asm/page.h>
 #include <asm/pgtable.h>
-- 
2.43.0