Re: [kvm-unit-tests PATCH v1 1/4] lib: s390x: add support for SCLP console read

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On 4/11/22 12:07, Nico Boehr wrote:
Add a basic implementation for reading from the SCLP ACII 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.

How much pain would it be to add the line mode read?


Signed-off-by: Nico Boehr <nrb@xxxxxxxxxxxxx>
---
[..]
+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 +240,59 @@ void sclp_print(const char *str)
  	sclp_print_ascii(str);
  	sclp_print_lm(str);
  }
+
+#define SCLP_EVENT_ASCII_DATA_STREAM_FOLLOWS 0

-> sclp.h

+
+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;

Reverse Christmas tree
The const int variables are all caps because they are essentially constants?

+
+	sclp_console_enable_read();
+
+	sclp_mark_busy();
+	memset(sccb, 0, 4096);

sizeof(*sccb)

+	sccb->h.length = PAGE_SIZE;
+	sccb->h.function_code = SCLP_UNCONDITIONAL_READ;
+	sccb->h.control_mask[2] = 0x80;
+
+	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_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;
+
+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..5bd1741d721d 100644
--- a/lib/s390x/sclp.h
+++ b/lib/s390x/sclp.h
@@ -313,6 +313,13 @@ typedef struct ReadEventData {
  	uint32_t mask;
  } __attribute__((packed)) ReadEventData;
+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 53b0fe044fe7..62e197cb93d7 100644
--- a/s390x/Makefile
+++ b/s390x/Makefile
@@ -71,6 +71,7 @@ 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




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