s390: sclp ascii console support

This code adds console support  by implementing SCLP's ASCII Console
Data event. This is the same console as LPARs ASCII console or z/VMs
sysascii.

The console can be specified manually with something like
-chardev stdio,id=charconsole0 -device sclpconsole,chardev=charconsole0,id=console0

Newer kernels will autodetect that console and prefer that over virtio
console.

When data is received from the character layer it creates a service
interrupt to trigger a Read Event Data command from the guest that will
pick up the received character byte-stream.
When characters are echo'ed by the linux guest a Write Event Data occurs
which is forwarded by the Event Facility to the console that supports
a corresponding mask value.
Console resizing is not supported.
The character layer byte-stream is buffered using a fixed size iov
buffer.

Signed-off-by: Heinz Graalfs <graalfs@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
Signed-off-by: Alexander Graf <agraf@suse.de>

hw/s390x/Makefile.objs

@@ -3,4 +3,4 @@ obj-y = s390-virtio-bus.o s390-virtio.o
 obj-y := $(addprefix ../,$(obj-y))
 obj-y += sclp.o
 obj-y += event-facility.o
-obj-y += sclpquiesce.o
+obj-y += sclpquiesce.o sclpconsole.o

hw/s390x/sclpconsole.c

@@ -0,0 +1,306 @@
+/*
+ * SCLP event type
+ *    Ascii Console Data (VT220 Console)
+ *
+ * Copyright IBM, Corp. 2012
+ *
+ * Authors:
+ *  Heinz Graalfs <graalfs@de.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or (at your
+ * option) any later version.  See the COPYING file in the top-level directory.
+ *
+ */
+
+#include <hw/qdev.h>
+#include "qemu-thread.h"
+
+#include "sclp.h"
+#include "event-facility.h"
+
+typedef struct ASCIIConsoleData {
+    EventBufferHeader ebh;
+    char data[0];
+} QEMU_PACKED ASCIIConsoleData;
+
+/* max size for ASCII data in 4K SCCB page */
+#define SIZE_BUFFER_VT220 4080
+
+typedef struct SCLPConsole {
+    SCLPEvent event;
+    CharDriverState *chr;
+    /* io vector                                                       */
+    uint8_t *iov;           /* iov buffer pointer                      */
+    uint8_t *iov_sclp;      /* pointer to SCLP read offset             */
+    uint8_t *iov_bs;        /* pointer byte stream read offset         */
+    uint32_t iov_data_len;  /* length of byte stream in buffer         */
+    uint32_t iov_sclp_rest; /* length of byte stream not read via SCLP */
+    qemu_irq irq_read_vt220;
+} SCLPConsole;
+
+/* character layer call-back functions */
+
+/* Return number of bytes that fit into iov buffer */
+static int chr_can_read(void *opaque)
+{
+    int can_read;
+    SCLPConsole *scon = opaque;
+
+    can_read = SIZE_BUFFER_VT220 - scon->iov_data_len;
+
+    return can_read;
+}
+
+/* Receive n bytes from character layer, save in iov buffer,
+ * and set event pending */
+static void receive_from_chr_layer(SCLPConsole *scon, const uint8_t *buf,
+                                   int size)
+{
+    assert(scon->iov);
+
+    /* read data must fit into current buffer */
+    assert(size <= SIZE_BUFFER_VT220 - scon->iov_data_len);
+
+    /* put byte-stream from character layer into buffer */
+    memcpy(scon->iov_bs, buf, size);
+    scon->iov_data_len += size;
+    scon->iov_sclp_rest += size;
+    scon->iov_bs += size;
+    scon->event.event_pending = true;
+}
+
+/* Send data from a char device over to the guest */
+static void chr_read(void *opaque, const uint8_t *buf, int size)
+{
+    SCLPConsole *scon = opaque;
+
+    assert(scon);
+
+    receive_from_chr_layer(scon, buf, size);
+    /* trigger SCLP read operation */
+    qemu_irq_raise(scon->irq_read_vt220);
+}
+
+static void chr_event(void *opaque, int event)
+{
+    SCLPConsole *scon = opaque;
+
+    switch (event) {
+    case CHR_EVENT_OPENED:
+        if (!scon->iov) {
+            scon->iov = g_malloc0(SIZE_BUFFER_VT220);
+            scon->iov_sclp = scon->iov;
+            scon->iov_bs = scon->iov;
+            scon->iov_data_len = 0;
+            scon->iov_sclp_rest = 0;
+        }
+        break;
+    case CHR_EVENT_CLOSED:
+        if (scon->iov) {
+            g_free(scon->iov);
+            scon->iov = NULL;
+        }
+        break;
+    }
+}
+
+/* functions to be called by event facility */
+
+static int event_type(void)
+{
+    return SCLP_EVENT_ASCII_CONSOLE_DATA;
+}
+
+static unsigned int send_mask(void)
+{
+    return SCLP_EVENT_MASK_MSG_ASCII;
+}
+
+static unsigned int receive_mask(void)
+{
+    return SCLP_EVENT_MASK_MSG_ASCII;
+}
+
+/* triggered by SCLP's read_event_data -
+ * copy console data byte-stream into provided (SCLP) buffer
+ */
+static void get_console_data(SCLPEvent *event, uint8_t *buf, size_t *size,
+                             int avail)
+{
+    SCLPConsole *cons = DO_UPCAST(SCLPConsole, event, event);
+
+    /* first byte is hex 0 saying an ascii string follows */
+    *buf++ = '\0';
+    avail--;
+    /* if all data fit into provided SCLP buffer */
+    if (avail >= cons->iov_sclp_rest) {
+        /* copy character byte-stream to SCLP buffer */
+        memcpy(buf, cons->iov_sclp, cons->iov_sclp_rest);
+        *size = cons->iov_sclp_rest + 1;
+        cons->iov_sclp = cons->iov;
+        cons->iov_bs = cons->iov;
+        cons->iov_data_len = 0;
+        cons->iov_sclp_rest = 0;
+        event->event_pending = false;
+        /* data provided and no more data pending */
+    } else {
+        /* if provided buffer is too small, just copy part */
+        memcpy(buf, cons->iov_sclp, avail);
+        *size = avail + 1;
+        cons->iov_sclp_rest -= avail;
+        cons->iov_sclp += avail;
+        /* more data pending */
+    }
+}
+
+static int read_event_data(SCLPEvent *event, EventBufferHeader *evt_buf_hdr,
+                           int *slen)
+{
+    int avail;
+    size_t src_len;
+    uint8_t *to;
+    ASCIIConsoleData *acd = (ASCIIConsoleData *) evt_buf_hdr;
+
+    if (!event->event_pending) {
+        /* no data pending */
+        return 0;
+    }
+
+    to = (uint8_t *)&acd->data;
+    avail = *slen - sizeof(ASCIIConsoleData);
+    get_console_data(event, to, &src_len, avail);
+
+    acd->ebh.length = cpu_to_be16(sizeof(ASCIIConsoleData) + src_len);
+    acd->ebh.type = SCLP_EVENT_ASCII_CONSOLE_DATA;
+    acd->ebh.flags |= SCLP_EVENT_BUFFER_ACCEPTED;
+    *slen = avail - src_len;
+
+    return 1;
+}
+
+/* triggered by SCLP's write_event_data
+ *  - write console data into character layer
+ *  returns < 0 if an error occured
+ */
+static ssize_t write_console_data(SCLPEvent *event, const uint8_t *buf,
+                                  size_t len)
+{
+    ssize_t ret = 0;
+    const uint8_t *iov_offset;
+    SCLPConsole *scon = DO_UPCAST(SCLPConsole, event, event);
+
+    if (!scon->chr) {
+        /* If there's no backend, we can just say we consumed all data. */
+        return len;
+    }
+
+    iov_offset = buf;
+    while (len > 0) {
+        ret = qemu_chr_fe_write(scon->chr, buf, len);
+        if (ret == 0) {
+            /* a pty doesn't seem to be connected - no error */
+            len = 0;
+        } else if (ret == -EAGAIN || (ret > 0 && ret < len)) {
+            len -= ret;
+            iov_offset += ret;
+        } else {
+            len = 0;
+        }
+    }
+
+    return ret;
+}
+
+static int write_event_data(SCLPEvent *event, EventBufferHeader *evt_buf_hdr)
+{
+    int rc;
+    int length;
+    ssize_t written;
+    ASCIIConsoleData *acd = (ASCIIConsoleData *) evt_buf_hdr;
+
+    length = be16_to_cpu(evt_buf_hdr->length) - sizeof(EventBufferHeader);
+    written = write_console_data(event, (uint8_t *)acd->data, length);
+
+    rc = SCLP_RC_NORMAL_COMPLETION;
+    /* set event buffer accepted flag */
+    evt_buf_hdr->flags |= SCLP_EVENT_BUFFER_ACCEPTED;
+
+    /* written will be zero if a pty is not connected - don't treat as error */
+    if (written < 0) {
+        /* event buffer not accepted due to error in character layer */
+        evt_buf_hdr->flags &= ~(SCLP_EVENT_BUFFER_ACCEPTED);
+        rc = SCLP_RC_CONTAINED_EQUIPMENT_CHECK;
+    }
+
+    return rc;
+}
+
+static void trigger_ascii_console_data(void *env, int n, int level)
+{
+    sclp_service_interrupt(0);
+}
+
+/* qemu object creation and initialization functions */
+
+/* tell character layer our call-back functions */
+static int console_init(SCLPEvent *event)
+{
+    static bool console_available;
+
+    SCLPConsole *scon = DO_UPCAST(SCLPConsole, event, event);
+
+    if (console_available) {
+        error_report("Multiple VT220 operator consoles are not supported");
+        return -1;
+    }
+    console_available = true;
+    event->event_type = SCLP_EVENT_ASCII_CONSOLE_DATA;
+    if (scon->chr) {
+        qemu_chr_add_handlers(scon->chr, chr_can_read,
+                              chr_read, chr_event, scon);
+    }
+    scon->irq_read_vt220 = *qemu_allocate_irqs(trigger_ascii_console_data,
+                                               NULL, 1);
+
+    return 0;
+}
+
+static int console_exit(SCLPEvent *event)
+{
+    return 0;
+}
+
+static Property console_properties[] = {
+    DEFINE_PROP_CHR("chardev", SCLPConsole, chr),
+    DEFINE_PROP_END_OF_LIST(),
+};
+
+static void console_class_init(ObjectClass *klass, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+    SCLPEventClass *ec = SCLP_EVENT_CLASS(klass);
+
+    dc->props = console_properties;
+    ec->init = console_init;
+    ec->exit = console_exit;
+    ec->get_send_mask = send_mask;
+    ec->get_receive_mask = receive_mask;
+    ec->event_type = event_type;
+    ec->read_event_data = read_event_data;
+    ec->write_event_data = write_event_data;
+}
+
+static TypeInfo sclp_console_info = {
+    .name          = "sclpconsole",
+    .parent        = TYPE_SCLP_EVENT,
+    .instance_size = sizeof(SCLPConsole),
+    .class_init    = console_class_init,
+    .class_size    = sizeof(SCLPEventClass),
+};
+
+static void register_types(void)
+{
+    type_register_static(&sclp_console_info);
+}
+
+type_init(register_types)