Re: [Qemu-devel] RFC adding ioctl's to virtserial/virtconsole

[Anthony Liguori]

On 08/02/2010 12:28 PM, Alon Levy wrote:
> ----- "Anthony Liguori"<address@hidden>  wrote:
>
>    
> > On 08/02/2010 03:33 AM, Alon Levy wrote:
> >      
> > > Hi,
> > >
> > >    This patch adds three CHR_IOCTLs and uses them in virtserial
> > >        
> > devices, to be used
> >      
> > > by a chardev backend, such as a spice vm channel (spice is a vdi
> > >        
> > solution).
> >      
> > >    Basically virtio-serial provides three driver initiated events for
> > >        
> > guest open of
> >      
> > > a device, guest close, and guest ready (driver port init complete)
> > >        
> > that before this
> >      
> > > patch are not exposed to the chardev backend.
> > >
> > >    With the spicevmc backend this is used like this:
> > > qemu -chardev spicevmc,id=vdiport,name=vdiport -device
> > >        
> > virtserialport,chardev=vdiport,name=com.redhat.spice.0
> >      
> > >    I'd appreciate any feedback if this seems the right way to
> > >        
> > accomplish this, and
> >      
> > > for the numbers I grabbed.
> > >
> > >        
> > I really hate to add connection semantics via IOCTLs.  I would rather
> > we
> > add them as first class semantics to the char device layer.  This
> > would
> > allow us to use char devices for VNC, for instance.
> >
> >      
> Ok, that's actually what I wanted to do at first, how about:
>    

My main objection to ioctls is that you change states based on event 
delivery.  This results in weird things like what happens when you do a 
chr_write while not ready or not connected.

So what I'd rather see is a move to an API that was connection 
oriented.  For instance, we could treat CharDriverState as an 
established connection.  So something like:

typedef struct CharServerState
{
   int backlog; /* max simultaneous connections; -1 for unlimited */
   void (*connect)(CharServerState *s, CharDriverState *session);
   void (*disconnect)(CharServerState *s, CharDriverState *session);
} CharDriverState;

Obviously, more thought is needed but I hope the point comes across.  We 
should be able to reflect the connect/disconnect semantics with an 
object that has a life cycle that matches the session instead of forcing 
each user to keep track of the session's life cycle.

Regards,

Anthony Liguori

> diff --git a/qemu-char.h b/qemu-char.h
> index 1df53ae..22973cd 100644
> --- a/qemu-char.h
> +++ b/qemu-char.h
> @@ -16,6 +16,8 @@
>   #define CHR_EVENT_MUX_OUT 4 /* mux-focus will move on */
>   #define CHR_EVENT_CLOSED  5 /* connection closed */
>
> +#define CHR_DEVICE_EVENT_OPENED 0
> +#define CHR_DEVICE_EVENT_CLOSED 1
>
>   #define CHR_IOCTL_SERIAL_SET_PARAMS   1
>   typedef struct {
> @@ -59,6 +61,7 @@ struct CharDriverState {
>       int (*chr_write)(struct CharDriverState *s, const uint8_t *buf, int len);
>       void (*chr_update_read_handler)(struct CharDriverState *s);
>       int (*chr_ioctl)(struct CharDriverState *s, int cmd, void *arg);
> +    int (*chr_device_event)(struct CharDriverState *s, int cmd, void *arg);
>       int (*get_msgfd)(struct CharDriverState *s);
>       IOEventHandler *chr_event;
>       IOCanReadHandler *chr_can_read;
> @@ -83,6 +86,7 @@ void qemu_chr_close(CharDriverState *chr);
>   void qemu_chr_printf(CharDriverState *s, const char *fmt, ...);
>   int qemu_chr_write(CharDriverState *s, const uint8_t *buf, int len);
>   void qemu_chr_send_event(CharDriverState *s, int event);
> +void qemu_chr_send_device_event(CharDriverState *s, int event, void *arg);
>   void qemu_chr_add_handlers(CharDriverState *s,
>                              IOCanReadHandler *fd_can_read,
>                              IOReadHandler *fd_read,
>
>
>    
> > Regards,
> >
> > Anthony Liguori
> >
> >      
> > > Alon
> > >
> > > -------------- commit message --------------------------------
> > >   From a90d4e26df727ed0d2b64b705e955f695289fa61 Mon Sep 17 00:00:00
> > >        
> > 2001
> >      
> > > From: Alon Levy<address@hidden>
> > > Date: Mon, 2 Aug 2010 11:22:58 +0300
> > > Subject: [PATCH] virtio-console: add IOCTL's for
> > >        
> > guest_{ready,open,close}
> >      
> > > Add three IOCTL corresponding to the three control events of:
> > >    guest_ready ->   CHR_IOCTL_VIRT_SERIAL_READY
> > >    guest_open  ->   CHR_IOCTL_VIRT_SERIAL_OPEN
> > >    guest_close ->   CHR_IOCTL_VIRT_SERIAL_CLOSE
> > >
> > > Can be used by a matching backend.
> > > ---
> > >    hw/virtio-console.c |   33 +++++++++++++++++++++++++++++++++
> > >    qemu-char.h         |    4 ++++
> > >    2 files changed, 37 insertions(+), 0 deletions(-)
> > >
> > > diff --git a/hw/virtio-console.c b/hw/virtio-console.c
> > > index caea11f..4c3686d 100644
> > > --- a/hw/virtio-console.c
> > > +++ b/hw/virtio-console.c
> > > @@ -58,6 +58,33 @@ static void chr_event(void *opaque, int event)
> > >        }
> > >    }
> > >
> > > +static void virtconsole_guest_open(VirtIOSerialPort *port)
> > > +{
> > > +    VirtConsole *vcon = DO_UPCAST(VirtConsole, port, port);
> > > +
> > > +    if (vcon->chr) {
> > > +        qemu_chr_ioctl(vcon->chr, CHR_IOCTL_VIRT_SERIAL_OPEN,
> > >        
> > NULL);
> >      
> > > +    }
> > > +}
> > > +
> > > +static void virtconsole_guest_close(VirtIOSerialPort *port)
> > > +{
> > > +    VirtConsole *vcon = DO_UPCAST(VirtConsole, port, port);
> > > +
> > > +    if (vcon->chr) {
> > > +        qemu_chr_ioctl(vcon->chr, CHR_IOCTL_VIRT_SERIAL_CLOSE,
> > >        
> > NULL);
> >      
> > > +    }
> > > +}
> > > +
> > > +static void virtconsole_guest_ready(VirtIOSerialPort *port)
> > > +{
> > > +    VirtConsole *vcon = DO_UPCAST(VirtConsole, port, port);
> > > +
> > > +    if (vcon->chr) {
> > > +        qemu_chr_ioctl(vcon->chr, CHR_IOCTL_VIRT_SERIAL_READY,
> > >        
> > NULL);
> >      
> > > +    }
> > > +}
> > > +
> > >    /* Virtio Console Ports */
> > >    static int virtconsole_initfn(VirtIOSerialDevice *dev)
> > >    {
> > > @@ -94,6 +121,9 @@ static VirtIOSerialPortInfo virtconsole_info = {
> > >        .qdev.size     = sizeof(VirtConsole),
> > >        .init          = virtconsole_initfn,
> > >        .exit          = virtconsole_exitfn,
> > > +    .guest_open    = virtconsole_guest_open,
> > > +    .guest_close   = virtconsole_guest_close,
> > > +    .guest_ready   = virtconsole_guest_ready,
> > >        .qdev.props = (Property[]) {
> > >            DEFINE_PROP_UINT8("is_console", VirtConsole,
> > >        
> > port.is_console, 1),
> >      
> > >            DEFINE_PROP_UINT32("nr", VirtConsole, port.id,
> > >        
> > VIRTIO_CONSOLE_BAD_ID),
> >      
> > > @@ -130,6 +160,9 @@ static VirtIOSerialPortInfo virtserialport_info
> > >        
> > = {
> >      
> > >        .qdev.size     = sizeof(VirtConsole),
> > >        .init          = virtserialport_initfn,
> > >        .exit          = virtconsole_exitfn,
> > > +    .guest_open    = virtconsole_guest_open,
> > > +    .guest_close   = virtconsole_guest_close,
> > > +    .guest_ready   = virtconsole_guest_ready,
> > >        .qdev.props = (Property[]) {
> > >            DEFINE_PROP_UINT32("nr", VirtConsole, port.id,
> > >        
> > VIRTIO_CONSOLE_BAD_ID),
> >      
> > >            DEFINE_PROP_CHR("chardev", VirtConsole, chr),
> > > diff --git a/qemu-char.h b/qemu-char.h
> > > index e3a0783..1df53ae 100644
> > > --- a/qemu-char.h
> > > +++ b/qemu-char.h
> > > @@ -41,6 +41,10 @@ typedef struct {
> > >    #define CHR_IOCTL_SERIAL_SET_TIOCM   13
> > >    #define CHR_IOCTL_SERIAL_GET_TIOCM   14
> > >
> > > +#define CHR_IOCTL_VIRT_SERIAL_OPEN   15
> > > +#define CHR_IOCTL_VIRT_SERIAL_CLOSE  16
> > > +#define CHR_IOCTL_VIRT_SERIAL_READY  17
> > > +
> > >    #define CHR_TIOCM_CTS        0x020
> > >    #define CHR_TIOCM_CAR        0x040
> > >    #define CHR_TIOCM_DSR        0x100
> > >
> > >