Patchwork [v4,06/07] s390: sclp ascii console support

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Submitter Christian Borntraeger
Date July 26, 2012, 8:55 a.m.
Message ID <1343292959-18308-1-git-send-email-borntraeger@de.ibm.com>
Download mbox | patch
Permalink /patch/173374/
State New
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Comments

Christian Borntraeger - July 26, 2012, 8:55 a.m.
From: Heinz Graalfs <graalfs@linux.vnet.ibm.com>

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.

changes in v4: fold in suggestions by blueswirl

Signed-off-by: Heinz Graalfs <graalfs@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
---
 hw/s390x/Makefile.objs |    2 +-
 hw/s390x/sclpconsole.c |  323 ++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 324 insertions(+), 1 deletions(-)
 create mode 100644 hw/s390x/sclpconsole.c
Alexander Graf - July 30, 2012, 2:02 p.m.
On 26.07.2012, at 10:55, Christian Borntraeger wrote:

> From: Heinz Graalfs <graalfs@linux.vnet.ibm.com>
> 
> 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.
> 
> changes in v4: fold in suggestions by blueswirl
> 
> Signed-off-by: Heinz Graalfs <graalfs@linux.vnet.ibm.com>
> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
> ---
> hw/s390x/Makefile.objs |    2 +-
> hw/s390x/sclpconsole.c |  323 ++++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 324 insertions(+), 1 deletions(-)
> create mode 100644 hw/s390x/sclpconsole.c
> 
> diff --git a/hw/s390x/Makefile.objs b/hw/s390x/Makefile.objs
> index ed4e61a..096dfcd 100644
> --- a/hw/s390x/Makefile.objs
> +++ b/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
> diff --git a/hw/s390x/sclpconsole.c b/hw/s390x/sclpconsole.c
> new file mode 100644
> index 0000000..c77b2a1
> --- /dev/null
> +++ b/hw/s390x/sclpconsole.c
> @@ -0,0 +1,323 @@
> +/*
> + * 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 sclp_read_vt220;

I'm sure this one wants a name that indicates it's an irq line ;)

> +} 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;
> +
> +    qemu_mutex_lock(&scon->event.lock);

Explicit locks now?

> +    can_read = SIZE_BUFFER_VT220 - scon->iov_data_len;
> +    qemu_mutex_unlock(&scon->event.lock);
> +
> +    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);
> +
> +    qemu_mutex_lock(&scon->event.lock);
> +
> +    /* if new data do not fit into current buffer */
> +    if (scon->iov_data_len + size > SIZE_BUFFER_VT220) {
> +        /* character layer sent more than allowed */
> +        qemu_mutex_unlock(&scon->event.lock);
> +        return;

So we drop the bytes it did send? Isn't there usually some can_read function from the char layer that we can indicate to that we have enough space?

If so, then this should be an assert(), right?

> +    }
> +    /* 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;
> +
> +    qemu_mutex_unlock(&scon->event.lock);
> +}
> +
> +/* 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->sclp_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 */
> +    }
> +}

I'm wondering whether we actually need this indirection from

  chr layer -> buffer -> sclp buffer.

Why can't we just do

  chr layer -> sclp buffer?


Alex
Christian Borntraeger - July 31, 2012, 1:05 p.m.
On 30/07/12 16:02, Alexander Graf wrote:

>> +    qemu_irq sclp_read_vt220;
> 
> I'm sure this one wants a name that indicates it's an irq line ;)

ok.

> 
>> +} 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;
>> +
>> +    qemu_mutex_lock(&scon->event.lock);
> 
> Explicit locks now?

IIRC Heinz introduced the locks since we have multiple threads working on the same
kind of buffers (the cpu threads and the main thread). We could not verify that the
main thread has the big qemu lock in all cases. Furthermore, this makes the code already
thread safe if we get rid of the big qemu lock somewhen. But I agree, we have to double
check why there are two different kind of locks.

[...]

>> +    /* if new data do not fit into current buffer */
>> +    if (scon->iov_data_len + size > SIZE_BUFFER_VT220) {
>> +        /* character layer sent more than allowed */
>> +        qemu_mutex_unlock(&scon->event.lock);
>> +        return;
> 
> So we drop the bytes it did send? Isn't there usually some can_read function from the char layer that we can indicate to that we have enough space?
> 
> If so, then this should be an assert(), right?

Probably yes. Will double check.

[..]

>> +    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 */
>> +    }
>> +}
> 
> I'm wondering whether we actually need this indirection from
> 
>   chr layer -> buffer -> sclp buffer.
> 
> Why can't we just do
> 
>   chr layer -> sclp buffer?
> 

The sclp interface is a bit different here. On an input event, the hw generated an service
interrupt with the event pending bit set. Then the guest kernel does a read event data sclp
call with input buffer. The input data has to copied into that and then returned via an
additional interrupt. 

Without the buffering our can_read function could only return 0 as size since there is yet no
buffer. Makes sense? 

Christian

Patch

diff --git a/hw/s390x/Makefile.objs b/hw/s390x/Makefile.objs
index ed4e61a..096dfcd 100644
--- a/hw/s390x/Makefile.objs
+++ b/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
diff --git a/hw/s390x/sclpconsole.c b/hw/s390x/sclpconsole.c
new file mode 100644
index 0000000..c77b2a1
--- /dev/null
+++ b/hw/s390x/sclpconsole.c
@@ -0,0 +1,323 @@ 
+/*
+ * 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 sclp_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;
+
+    qemu_mutex_lock(&scon->event.lock);
+    can_read = SIZE_BUFFER_VT220 - scon->iov_data_len;
+    qemu_mutex_unlock(&scon->event.lock);
+
+    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);
+
+    qemu_mutex_lock(&scon->event.lock);
+
+    /* if new data do not fit into current buffer */
+    if (scon->iov_data_len + size > SIZE_BUFFER_VT220) {
+        /* character layer sent more than allowed */
+        qemu_mutex_unlock(&scon->event.lock);
+        return;
+    }
+    /* 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;
+
+    qemu_mutex_unlock(&scon->event.lock);
+}
+
+/* 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->sclp_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;
+
+    qemu_mutex_lock(&event->lock);
+
+    if (!event->event_pending) {
+        /* no data pending */
+        qemu_mutex_unlock(&event->lock);
+        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;
+
+    qemu_mutex_unlock(&event->lock);
+
+    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->sclp_read_vt220 = *qemu_allocate_irqs(trigger_ascii_console_data,
+                                                NULL, 1);
+
+    qemu_mutex_init(&event->lock);
+
+    return 0;
+}
+
+static int console_exit(SCLPEvent *event)
+{
+    qemu_mutex_destroy(&event->lock);
+
+    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)