Re: [PATCH v5 4/9] ui/vdagent: core infrastructure

["Marc-André Lureau" <marcandre.lureau@gmail.com>]

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Hi

On Tue, May 11, 2021 at 1:04 PM Gerd Hoffmann <kraxel@redhat.com> wrote:

> > > +/* ------------------------------------------------------------------
> */
> > > +/* send messages
> */
> > > +
> > > +static void vdagent_send_buf(VDAgentChardev *vd, void *ptr, uint32_t
> > > msgsize)
> > > +{
> > > +    uint8_t *msgbuf = ptr;
> > > +    uint32_t len, pos = 0;
> > > +
> > > +    while (pos < msgsize) {
> > > +        len = qemu_chr_be_can_write(CHARDEV(vd));
> > > +        if (len > msgsize - pos) {
> > > +            len = msgsize - pos;
> > > +        }
> > > +        qemu_chr_be_write(CHARDEV(vd), msgbuf + pos, len);
> > > +        pos += len;
> > > +    }
> > >
> >
> > This looks like it could easily busy loop. Have you thought about fixing
> > this?
>
> Incremental fix [ to be squashed ]
>
>
thanks, a few comments below

take care,
>   Gerd
>
> diff --git a/ui/vdagent.c b/ui/vdagent.c
> index 64213aa25a06..efa98725fb22 100644
> --- a/ui/vdagent.c
> +++ b/ui/vdagent.c
> @@ -3,7 +3,9 @@
>  #include "include/qemu-common.h"
>  #include "chardev/char.h"
>  #include "hw/qdev-core.h"
> +#include "qemu/buffer.h"
>  #include "qemu/option.h"
> +#include "qemu/units.h"
>  #include "ui/clipboard.h"
>  #include "ui/console.h"
>  #include "ui/input.h"
> @@ -16,6 +18,7 @@
>
>  #define VDAGENT_MOUSE_DEFAULT true
>  #define VDAGENT_CLIPBOARD_DEFAULT false
> +#define VDAGENT_BUFFER_LIMIT (1 * MiB)
>
>  struct VDAgentChardev {
>      Chardev parent;
> @@ -32,6 +35,7 @@ struct VDAgentChardev {
>      uint32_t msgsize;
>      uint8_t *xbuf;
>      uint32_t xoff, xsize;
> +    Buffer outbuf;
>
>      /* mouse */
>      DeviceState mouse_dev;
> @@ -124,18 +128,20 @@ static const char *type_name[] = {
>  /* ------------------------------------------------------------------ */
>  /* send messages                                                      */
>
> -static void vdagent_send_buf(VDAgentChardev *vd, void *ptr, uint32_t
> msgsize)
> +static void vdagent_send_buf(VDAgentChardev *vd)
>  {
> -    uint8_t *msgbuf = ptr;
> -    uint32_t len, pos = 0;
> +    uint32_t len;
>
> -    while (pos < msgsize) {
> +    while (!buffer_empty(&vd->outbuf)) {
>          len = qemu_chr_be_can_write(CHARDEV(vd));
> -        if (len > msgsize - pos) {
> -            len = msgsize - pos;
> +        if (len == 0) {
> +            return;
>          }
> -        qemu_chr_be_write(CHARDEV(vd), msgbuf + pos, len);
> -        pos += len;
> +        if (len > vd->outbuf.offset) {
> +            len = vd->outbuf.offset;
> +        }
> +        qemu_chr_be_write(CHARDEV(vd), vd->outbuf.buffer, len);
> +        buffer_advance(&vd->outbuf, len);
>      }
>  }
>
> @@ -150,16 +156,22 @@ static void vdagent_send_msg(VDAgentChardev *vd,
> VDAgentMessage *msg)
>
>      msg->protocol = VD_AGENT_PROTOCOL;
>
> +    if (vd->outbuf.offset + msgsize > VDAGENT_BUFFER_LIMIT) {
> +        return;
> +    }
>

Silently dropping messages, there might be some bad consequences. At least
I think we should error_report(). Eventually, the caller should be informed
too.


> +
>      while (msgoff < msgsize) {
>          chunk.port = VDP_CLIENT_PORT;
>          chunk.size = msgsize - msgoff;
>          if (chunk.size > 1024) {
>              chunk.size = 1024;
>          }
> -        vdagent_send_buf(vd, &chunk, sizeof(chunk));
> -        vdagent_send_buf(vd, msgbuf + msgoff, chunk.size);
> +        buffer_reserve(&vd->outbuf, sizeof(chunk) + chunk.size);
> +        buffer_append(&vd->outbuf, &chunk, sizeof(chunk));
> +        buffer_append(&vd->outbuf, msgbuf + msgoff, chunk.size);
>          msgoff += chunk.size;
>      }
> +    vdagent_send_buf(vd);
>  }
>
>  static void vdagent_send_caps(VDAgentChardev *vd)
> @@ -550,6 +562,7 @@ static void vdagent_chr_open(Chardev *chr,
>
> &vdagent_mouse_handler);
>      }
>
> +    buffer_init(&vd->outbuf, "vdagent-outbuf");
>

Needs a buffer_free(). Move it to object init/finalize ?

     *be_opened = true;
>  }
>
> @@ -702,6 +715,13 @@ static int vdagent_chr_write(Chardev *chr, const
> uint8_t *buf, int len)
>      return ret;
>  }
>
> +static void vdagent_chr_accept_input(Chardev *chr)
> +{
> +    VDAgentChardev *vd = QEMU_VDAGENT_CHARDEV(chr);
> +
> +    vdagent_send_buf(vd);
> +}
> +
>  static void vdagent_chr_set_fe_open(struct Chardev *chr, int fe_open)
>  {
>      VDAgentChardev *vd = QEMU_VDAGENT_CHARDEV(chr);
> @@ -748,6 +768,7 @@ static void vdagent_chr_class_init(ObjectClass *oc,
> void *data)
>      cc->open             = vdagent_chr_open;
>      cc->chr_write        = vdagent_chr_write;
>      cc->chr_set_fe_open  = vdagent_chr_set_fe_open;
> +    cc->chr_accept_input = vdagent_chr_accept_input;
>  }
>
>  static const TypeInfo vdagent_chr_type_info = {
> --
> 2.31.1
>
>

-- 
Marc-André Lureau

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