Re: [Qemu-devel] [PATCH 1/4] qemu-char: Add new char backend CirMemCharDriver

[Lei Li]

On 10/27/2012 12:47 AM, Luiz Capitulino wrote:
> On Fri, 26 Oct 2012 19:21:49 +0800
> Lei Li <address@hidden> wrote:
>
> > Signed-off-by: Lei Li <address@hidden>
> > ---
> >   qemu-char.c     |  140 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
> >   qemu-config.c   |    3 +
> >   qemu-options.hx |   10 ++++
> >   3 files changed, 153 insertions(+), 0 deletions(-)
> >
> > diff --git a/qemu-char.c b/qemu-char.c
> > index b082bae..c3ec43d 100644
> > --- a/qemu-char.c
> > +++ b/qemu-char.c
> > @@ -99,6 +99,7 @@
> >   #include "ui/qemu-spice.h"
> >   
> >   #define READ_BUF_LEN 4096
> > +#define CBUFF_SIZE 65536
> >   
> >   /***********************************************************/
> >   /* character device */
> > @@ -2588,6 +2589,134 @@ size_t qemu_chr_mem_osize(const CharDriverState *chr)
> >       return d->outbuf_size;
> >   }
> >   
> > +/*********************************************************/
> > +/*CircularMemory chardev*/
> > +
> > +typedef struct {
> > +    size_t size;
> > +    size_t producer;
> > +    size_t consumer;
> > +    uint8_t *cbuf;
> > +} CirMemCharDriver;
> > +
> > +static bool cirmem_chr_is_empty(const CharDriverState *chr)
> > +{
> > +    const CirMemCharDriver *d = chr->opaque;
> > +
> > +    return d->producer == d->consumer;
> > +}
> > +
> > +static bool cirmem_chr_is_full(const CharDriverState *chr)
> > +{
> > +    const CirMemCharDriver *d = chr->opaque;
> > +
> > +    return (d->producer - d->consumer) >= d->size;
> > +}
> > +
> > +static bool cirmem_chr_unlimit(const CharDriverState *chr)
> > +{
> > +    const CirMemCharDriver *d = chr->opaque;
> > +
> > +    return d->producer >= d->consumer;
> > +}
> I'm not sure I get why this is needed. Are you trying to fix the problem
> I mentioned in my last review that producer and consumer might overflow
> for long running VMs? If yes, then the problem still exists.
>
> The only fix I can think of is to re-initialize them. Of course that you
> could do it in a way that they keep pointing to the right position in cbuf[].
>
> > +
> > +static int cirmem_chr_write(CharDriverState *chr, const uint8_t *buf, int len)
> > +{
> > +    CirMemCharDriver *d = chr->opaque;
> > +    int i;
> > +
> > +    if (!buf || (len < 0)) {
> > +        return -1;
> > +    }
> > +
> > +    for (i = 0; i < len; i++ ) {
> > +        if (cirmem_chr_unlimit(chr)) {
> > +            /* Avoid writing the IAC information to the queue. */
> > +            if ((unsigned char)buf[i] == IAC) {
> > +                continue;
> > +            }
> > +            d->cbuf[d->producer % d->size] = buf[i];
> > +            d->producer++;
> > +        } else {
> > +            return -1;
> > +        }
> > +    }
> > +
> > +    return 0;
> > +}
> > +
> > +static int cirmem_chr_read(CharDriverState *chr, uint8_t *buf, int len)
> > +{
> > +    CirMemCharDriver *d = chr->opaque;
> > +    int i;
> > +
> > +    if (cirmem_chr_is_empty(chr) || len < 0) {
> > +        return -1;
> > +    }
> > +
> > +    if (len > d->size) {
> > +        len = d->size;
> > +    }
> > +
> > +    for (i = 0; i < len; i++) {
> > +        if (cirmem_chr_unlimit(chr)) {
> > +            buf[i] = d->cbuf[d->consumer % d->size];
> > +            d->consumer++;
> > +
> > +            if (cirmem_chr_is_empty(chr)) {
> > +                break;
> > +            }
> > +        } else {
> > +            return -1;
> > +        }
> > +    }
> > +
> > +    return 0;
> > +}
> > +
> > +static void cirmem_chr_close(struct CharDriverState *chr)
> > +{
> > +    CirMemCharDriver *d = chr->opaque;
> > +
> > +    g_free(d->cbuf);
> > +    g_free(d);
> > +    chr->opaque = NULL;
> > +}
> > +
> > +static CharDriverState *qemu_chr_open_cirmemchr(QemuOpts *opts)
> > +{
> > +    CharDriverState *chr;
> > +    CirMemCharDriver *d;
> > +
> > +    chr = g_malloc0(sizeof(CharDriverState));
> > +    d = g_malloc(sizeof(*d));
> > +
> > +    d->size = qemu_opt_get_number(opts, "maxcapacity", 0);
> > +    if (d->size == 0) {
> > +        d->size = CBUFF_SIZE;
> > +    }
> > +
> > +    /* The size must be power of 2 */
> If this is enforced in vl.c (which I can't remember right now), then
> you should turn this into an assert().

It is just enforced in here, not in vl.c.

> > +    if (d->size & (d->size - 1)) {
> > +        goto fail;
> > +    }
> > +
> > +    d->producer = 0;
> > +    d->consumer = 0;
> > +    d->cbuf = g_malloc0(d->size);
> > +
> > +    chr->opaque = d;
> > +    chr->chr_write = cirmem_chr_write;
> > +    chr->chr_close = cirmem_chr_close;
> > +
> > +    return chr;
> > +
> > +fail:
> > +    g_free(d);
> > +    g_free(chr);
> > +    return NULL;
> > +}
> > +
> >   QemuOpts *qemu_chr_parse_compat(const char *label, const char *filename)
> >   {
> >       char host[65], port[33], width[8], height[8];
> > @@ -2652,6 +2781,16 @@ QemuOpts *qemu_chr_parse_compat(const char *label, const 
> > char *filename)
> >           qemu_opt_set(opts, "path", p);
> >           return opts;
> >       }
> > +    if (strstart(filename, "memchr", &p)) {
> > +        qemu_opt_set(opts, "backend", "memchr");
> > +        qemu_opt_set(opts, "maxcapacity", p);
> > +        return opts;
> > +    }
> > +    if (strstart(filename, "memchr", &p)) {
> > +        qemu_opt_set(opts, "backend", "memchr");
> > +        qemu_opt_set(opts, "maxcapacity", p);
> > +        return opts;
> Duplication?

Yeah...

> > +    }
> >       if (strstart(filename, "tcp:", &p) ||
> >           strstart(filename, "telnet:", &p)) {
> >           if (sscanf(p, "%64[^:]:%32[^,]%n", host, port, &pos) < 2) {
> > @@ -2725,6 +2864,7 @@ static const struct {
> >       { .name = "udp",       .open = qemu_chr_open_udp },
> >       { .name = "msmouse",   .open = qemu_chr_open_msmouse },
> >       { .name = "vc",        .open = text_console_init },
> > +    { .name = "memchr",    .open = qemu_chr_open_cirmemchr },
> What about my suggestion of calling this "memory"? All backends here are
> chardevs, but we don't have vcchr, msmousechr, stdiochr etc.

Yes, it make sense.

> >   #ifdef _WIN32
> >       { .name = "file",      .open = qemu_chr_open_win_file_out },
> >       { .name = "pipe",      .open = qemu_chr_open_win_pipe },
> > diff --git a/qemu-config.c b/qemu-config.c
> > index cd1ec21..5553bb6 100644
> > --- a/qemu-config.c
> > +++ b/qemu-config.c
> > @@ -213,6 +213,9 @@ static QemuOptsList qemu_chardev_opts = {
> >           },{
> >               .name = "debug",
> >               .type = QEMU_OPT_NUMBER,
> > +        },{
> > +            .name = "maxcapacity",
> > +            .type = QEMU_OPT_NUMBER,
> >           },
> >           { /* end of list */ }
> >       },
> > diff --git a/qemu-options.hx b/qemu-options.hx
> > index 46f0539..9b2d792 100644
> > --- a/qemu-options.hx
> > +++ b/qemu-options.hx
> > @@ -1680,6 +1680,7 @@ DEF("chardev", HAS_ARG, QEMU_OPTION_chardev,
> >       "-chardev msmouse,id=id[,mux=on|off]\n"
> >       "-chardev 
> > vc,id=id[[,width=width][,height=height]][[,cols=cols][,rows=rows]]\n"
> >       "         [,mux=on|off]\n"
> > +    "-chardev memchr,id=id,maxcapacity=maxcapacity\n"
> >       "-chardev file,id=id,path=path[,mux=on|off]\n"
> >       "-chardev pipe,id=id,path=path[,mux=on|off]\n"
> >   #ifdef _WIN32
> > @@ -1718,6 +1719,7 @@ Backend is one of:
> >   @option{udp},
> >   @option{msmouse},
> >   @option{vc},
> > address@hidden,
> >   @option{file},
> >   @option{pipe},
> >   @option{console},
> > @@ -1824,6 +1826,14 @@ the console, in pixels.
> >   @option{cols} and @option{rows} specify that the console be sized to fit a 
> > text
> >   console with the given dimensions.
> >   
> > address@hidden -chardev memchr ,address@hidden ,address@hidden
> > +
> > +Create a circular buffer with fixed size indicated by optionally 
> > @option{maxcapacity}
> > +which will be default 64K if it is not given.
> > +
> > address@hidden specifies the max capacity of the size of circular buffer
> > +to create. Should be power of 2.
> > +
> >   @item -chardev file ,address@hidden ,address@hidden
> >   
> >   Log all traffic received from the guest to a file.


--
Lei