[kvm-unit-tests PATCH v2 1/4] lib: s390x: add support for SCLP console read

[Nico Boehr <nrb@linux.ibm.com>]

Add a basic implementation for reading from the SCLP ASCII console. The goal of
this is to support migration tests on s390x. To know when the migration has been
finished, we need to listen for a newline on our console.

Hence, this implementation is focused on the SCLP ASCII console of QEMU and
currently won't work under e.g. LPAR.

Signed-off-by: Nico Boehr <nrb@linux.ibm.com>
---
 lib/s390x/sclp-console.c | 79 +++++++++++++++++++++++++++++++++++++---
 lib/s390x/sclp.h         |  8 ++++
 s390x/Makefile           |  1 +
 3 files changed, 82 insertions(+), 6 deletions(-)

diff --git a/lib/s390x/sclp-console.c b/lib/s390x/sclp-console.c
index fa36a6a42381..e580de6830d6 100644
--- a/lib/s390x/sclp-console.c
+++ b/lib/s390x/sclp-console.c
@@ -89,6 +89,10 @@ static char lm_buff[120];
 static unsigned char lm_buff_off;
 static struct spinlock lm_buff_lock;
 
+static char read_buf[4096];
+static int read_index = sizeof(read_buf) - 1;
+static int read_buf_end = 0;
+
 static void sclp_print_ascii(const char *str)
 {
 	int len = strlen(str);
@@ -185,7 +189,7 @@ static void sclp_print_lm(const char *str)
  * indicating which messages the control program (we) want(s) to
  * send/receive.
  */
-static void sclp_set_write_mask(void)
+static void sclp_write_event_mask(int receive_mask, int send_mask)
 {
 	WriteEventMask *sccb = (void *)_sccb;
 
@@ -195,18 +199,27 @@ static void sclp_set_write_mask(void)
 	sccb->h.function_code = SCLP_FC_NORMAL_WRITE;
 	sccb->mask_length = sizeof(sccb_mask_t);
 
-	/* For now we don't process sclp input. */
-	sccb->cp_receive_mask = 0;
-	/* We send ASCII and line mode. */
-	sccb->cp_send_mask = SCLP_EVENT_MASK_MSG_ASCII | SCLP_EVENT_MASK_MSG;
+	sccb->cp_receive_mask = receive_mask;
+	sccb->cp_send_mask = send_mask;
 
 	sclp_service_call(SCLP_CMD_WRITE_EVENT_MASK, sccb);
 	assert(sccb->h.response_code == SCLP_RC_NORMAL_COMPLETION);
 }
 
+static void sclp_console_enable_read(void)
+{
+	sclp_write_event_mask(SCLP_EVENT_MASK_MSG_ASCII, SCLP_EVENT_MASK_MSG_ASCII | SCLP_EVENT_MASK_MSG);
+}
+
+static void sclp_console_disable_read(void)
+{
+	sclp_write_event_mask(0, SCLP_EVENT_MASK_MSG_ASCII | SCLP_EVENT_MASK_MSG);
+}
+
 void sclp_console_setup(void)
 {
-	sclp_set_write_mask();
+	/* We send ASCII and line mode. */
+	sclp_write_event_mask(0, SCLP_EVENT_MASK_MSG_ASCII | SCLP_EVENT_MASK_MSG);
 }
 
 void sclp_print(const char *str)
@@ -227,3 +240,57 @@ void sclp_print(const char *str)
 	sclp_print_ascii(str);
 	sclp_print_lm(str);
 }
+
+static int console_refill_read_buffer(void)
+{
+	const int max_event_buffer_len = SCCB_SIZE - offsetof(ReadEventDataAsciiConsole, ebh);
+	ReadEventDataAsciiConsole *sccb = (void *)_sccb;
+	const int event_buffer_ascii_recv_header_len = sizeof(sccb->ebh) + sizeof(sccb->type);
+	int ret = -1;
+
+	sclp_console_enable_read();
+
+	sclp_mark_busy();
+	memset(sccb, 0, SCCB_SIZE);
+	sccb->h.length = PAGE_SIZE;
+	sccb->h.function_code = SCLP_UNCONDITIONAL_READ;
+	sccb->h.control_mask[2] = SCLP_CM2_VARIABLE_LENGTH_RESPONSE;
+
+	sclp_service_call(SCLP_CMD_READ_EVENT_DATA, sccb);
+
+	if ((sccb->h.response_code == SCLP_RC_NO_EVENT_BUFFERS_STORED) ||
+	    (sccb->ebh.type != SCLP_EVENT_ASCII_CONSOLE_DATA) ||
+	    (sccb->type != SCLP_EVENT_ASCII_TYPE_DATA_STREAM_FOLLOWS)) {
+		ret = -1;
+		goto out;
+	}
+
+	assert(sccb->ebh.length <= max_event_buffer_len);
+	assert(sccb->ebh.length > event_buffer_ascii_recv_header_len);
+
+	read_buf_end = sccb->ebh.length - event_buffer_ascii_recv_header_len;
+
+	assert(read_buf_end <= sizeof(read_buf));
+	memcpy(read_buf, sccb->data, read_buf_end);
+
+	read_index = 0;
+	ret = 0;
+
+out:
+	sclp_console_disable_read();
+
+	return ret;
+}
+
+int __getchar(void)
+{
+	int ret;
+
+	if (read_index >= read_buf_end) {
+		ret = console_refill_read_buffer();
+		if (ret < 0)
+			return ret;
+	}
+
+	return read_buf[read_index++];
+}
diff --git a/lib/s390x/sclp.h b/lib/s390x/sclp.h
index fead007a6037..e48a5a3df20b 100644
--- a/lib/s390x/sclp.h
+++ b/lib/s390x/sclp.h
@@ -313,6 +313,14 @@ typedef struct ReadEventData {
 	uint32_t mask;
 } __attribute__((packed)) ReadEventData;
 
+#define SCLP_EVENT_ASCII_TYPE_DATA_STREAM_FOLLOWS 0
+typedef struct ReadEventDataAsciiConsole {
+	SCCBHeader h;
+	EventBufferHeader ebh;
+	uint8_t type;
+	char data[];
+} __attribute__((packed)) ReadEventDataAsciiConsole;
+
 extern char _sccb[];
 void sclp_setup_int(void);
 void sclp_handle_ext(void);
diff --git a/s390x/Makefile b/s390x/Makefile
index c11f6efbd767..f38f442b9cb1 100644
--- a/s390x/Makefile
+++ b/s390x/Makefile
@@ -75,6 +75,7 @@ cflatobjs += lib/alloc_phys.o
 cflatobjs += lib/alloc_page.o
 cflatobjs += lib/vmalloc.o
 cflatobjs += lib/alloc_phys.o
+cflatobjs += lib/getchar.o
 cflatobjs += lib/s390x/io.o
 cflatobjs += lib/s390x/stack.o
 cflatobjs += lib/s390x/sclp.o
-- 
2.31.1