Re: [Qemu-devel] [PATCH 6/8] slirp: VMStatify sbuf

[Samuel Thibault <samuel.thibault@gnu.org>]

Dr. David Alan Gilbert (git), on Thu 27 Oct 2016 16:32:15 +0100, wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> 
> Convert the sbuf structure to a VMStateDescription.
> Note this uses the VMSTATE_WITH_TMP mechanism to calculate
> and reload the offsets based on the pointers.
> 
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

Acked-by: Samuel Thibault <samuel.thibault@ens-lyon.org>

> ---
>  slirp/sbuf.h  |   4 +-
>  slirp/slirp.c | 116 ++++++++++++++++++++++++++++++++++++++--------------------
>  2 files changed, 78 insertions(+), 42 deletions(-)
> 
> diff --git a/slirp/sbuf.h b/slirp/sbuf.h
> index efcec39..a722ecb 100644
> --- a/slirp/sbuf.h
> +++ b/slirp/sbuf.h
> @@ -12,8 +12,8 @@
>  #define sbspace(sb) ((sb)->sb_datalen - (sb)->sb_cc)
>  
>  struct sbuf {
> -	u_int	sb_cc;		/* actual chars in buffer */
> -	u_int	sb_datalen;	/* Length of data  */
> +	uint32_t sb_cc;		/* actual chars in buffer */
> +	uint32_t sb_datalen;	/* Length of data  */
>  	char	*sb_wptr;	/* write pointer. points to where the next
>  				 * bytes should be written in the sbuf */
>  	char	*sb_rptr;	/* read pointer. points to where the next
> diff --git a/slirp/slirp.c b/slirp/slirp.c
> index 6276315..2f7802e 100644
> --- a/slirp/slirp.c
> +++ b/slirp/slirp.c
> @@ -1185,19 +1185,72 @@ static const VMStateDescription vmstate_slirp_tcp = {
>      }
>  };
>  
> -static void slirp_sbuf_save(QEMUFile *f, struct sbuf *sbuf)
> +/* The sbuf has a pair of pointers that are migrated as offsets;
> + * we calculate the offsets and restore the pointers using
> + * pre_save/post_load on a tmp structure.
> + */
> +struct sbuf_tmp {
> +    struct sbuf *parent;
> +    uint32_t roff, woff;
> +};
> +
> +static void sbuf_tmp_pre_save(void *opaque)
> +{
> +    struct sbuf_tmp *tmp = opaque;
> +    tmp->woff = tmp->parent->sb_wptr - tmp->parent->sb_data;
> +    tmp->roff = tmp->parent->sb_rptr - tmp->parent->sb_data;
> +}
> +
> +static int sbuf_tmp_post_load(void *opaque, int version)
>  {
> -    uint32_t off;
> -
> -    qemu_put_be32(f, sbuf->sb_cc);
> -    qemu_put_be32(f, sbuf->sb_datalen);
> -    off = (uint32_t)(sbuf->sb_wptr - sbuf->sb_data);
> -    qemu_put_sbe32(f, off);
> -    off = (uint32_t)(sbuf->sb_rptr - sbuf->sb_data);
> -    qemu_put_sbe32(f, off);
> -    qemu_put_buffer(f, (unsigned char*)sbuf->sb_data, sbuf->sb_datalen);
> +    struct sbuf_tmp *tmp = opaque;
> +    uint32_t requested_len = tmp->parent->sb_datalen;
> +
> +    /* Allocate the buffer space used by the field after the tmp */
> +    sbreserve(tmp->parent, tmp->parent->sb_datalen);
> +
> +    if (tmp->parent->sb_datalen != requested_len) {
> +        return -ENOMEM;
> +    }
> +    if (tmp->woff >= requested_len ||
> +        tmp->roff >= requested_len) {
> +        error_report("invalid sbuf offsets r/w=%u/%u len=%u",
> +                     tmp->roff, tmp->woff, requested_len);
> +        return -EINVAL;
> +    }
> +
> +    tmp->parent->sb_wptr = tmp->parent->sb_data + tmp->woff;
> +    tmp->parent->sb_rptr = tmp->parent->sb_data + tmp->roff;
> +
> +    return 0;
>  }
>  
> +
> +static const VMStateDescription vmstate_slirp_sbuf_tmp = {
> +    .name = "slirp-sbuf-tmp",
> +    .post_load = sbuf_tmp_post_load,
> +    .pre_save  = sbuf_tmp_pre_save,
> +    .version_id = 0,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_UINT32(woff, struct sbuf_tmp),
> +        VMSTATE_UINT32(roff, struct sbuf_tmp),
> +        VMSTATE_END_OF_LIST()
> +    }
> +};
> +
> +static const VMStateDescription vmstate_slirp_sbuf = {
> +    .name = "slirp-sbuf",
> +    .version_id = 0,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_UINT32(sb_cc, struct sbuf),
> +        VMSTATE_UINT32(sb_datalen, struct sbuf),
> +        VMSTATE_WITH_TMP(struct sbuf, struct sbuf_tmp, vmstate_slirp_sbuf_tmp),
> +        VMSTATE_VBUFFER_UINT32(sb_data, struct sbuf, 0, NULL, 0, sb_datalen),
> +        VMSTATE_END_OF_LIST()
> +    }
> +};
> +
> +
>  static void slirp_socket_save(QEMUFile *f, struct socket *so)
>  {
>      qemu_put_be32(f, so->so_urgc);
> @@ -1225,8 +1278,9 @@ static void slirp_socket_save(QEMUFile *f, struct socket *so)
>      qemu_put_byte(f, so->so_emu);
>      qemu_put_byte(f, so->so_type);
>      qemu_put_be32(f, so->so_state);
> -    slirp_sbuf_save(f, &so->so_rcv);
> -    slirp_sbuf_save(f, &so->so_snd);
> +    /* TODO: Build vmstate at this level */
> +    vmstate_save_state(f, &vmstate_slirp_sbuf, &so->so_rcv, 0);
> +    vmstate_save_state(f, &vmstate_slirp_sbuf, &so->so_snd, 0);
>      vmstate_save_state(f, &vmstate_slirp_tcp, so->so_tcpcb, 0);
>  }
>  
> @@ -1263,31 +1317,9 @@ static void slirp_state_save(QEMUFile *f, void *opaque)
>      slirp_bootp_save(f, slirp);
>  }
>  
> -static int slirp_sbuf_load(QEMUFile *f, struct sbuf *sbuf)
> -{
> -    uint32_t off, sb_cc, sb_datalen;
> -
> -    sb_cc = qemu_get_be32(f);
> -    sb_datalen = qemu_get_be32(f);
> -
> -    sbreserve(sbuf, sb_datalen);
> -
> -    if (sbuf->sb_datalen != sb_datalen)
> -        return -ENOMEM;
> -
> -    sbuf->sb_cc = sb_cc;
> -
> -    off = qemu_get_sbe32(f);
> -    sbuf->sb_wptr = sbuf->sb_data + off;
> -    off = qemu_get_sbe32(f);
> -    sbuf->sb_rptr = sbuf->sb_data + off;
> -    qemu_get_buffer(f, (unsigned char*)sbuf->sb_data, sbuf->sb_datalen);
> -
> -    return 0;
> -}
> -
>  static int slirp_socket_load(QEMUFile *f, struct socket *so, int version_id)
>  {
> +    int ret = 0;
>      if (tcp_attach(so) < 0)
>          return -ENOMEM;
>  
> @@ -1324,11 +1356,15 @@ static int slirp_socket_load(QEMUFile *f, struct socket *so, int version_id)
>      so->so_emu = qemu_get_byte(f);
>      so->so_type = qemu_get_byte(f);
>      so->so_state = qemu_get_be32(f);
> -    if (slirp_sbuf_load(f, &so->so_rcv) < 0)
> -        return -ENOMEM;
> -    if (slirp_sbuf_load(f, &so->so_snd) < 0)
> -        return -ENOMEM;
> -    return vmstate_load_state(f, &vmstate_slirp_tcp, so->so_tcpcb, 0);
> +    /* TODO: VMState at this level */
> +    ret = vmstate_load_state(f, &vmstate_slirp_sbuf, &so->so_rcv, 0);
> +    if (!ret) {
> +        ret = vmstate_load_state(f, &vmstate_slirp_sbuf, &so->so_snd, 0);
> +    }
> +    if (!ret) {
> +        ret = vmstate_load_state(f, &vmstate_slirp_tcp, so->so_tcpcb, 0);
> +    }
> +    return ret;
>  }
>  
>  static void slirp_bootp_load(QEMUFile *f, Slirp *slirp)
> -- 
> 2.9.3
> 

-- 
Samuel
"...very few phenomena can pull someone out of Deep Hack Mode, with two
noted exceptions: being struck by lightning, or worse, your *computer*
being struck by lightning."
(By Matt Welsh)