From mboxrd@z Thu Jan  1 00:00:00 1970
From: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Subject: Re: [PATCH 2/5] vhost: refactor virtio_dev_rx
Date: Mon, 14 Dec 2015 09:47:16 +0800
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Cc: dev@dpdk.org, Victor Kaplansky <vkaplans@redhat.com>,
 "Michael S. Tsirkin" <mst@redhat.com>
To: Rich Lane <rich.lane@bigswitch.com>
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On Fri, Dec 11, 2015 at 12:42:33PM -0800, Rich Lane wrote:
> On Wed, Dec 2, 2015 at 10:06 PM, Yuanhan Liu <yuanhan.liu@linux.intel.c=
om>
> wrote:
>=20
>     +static inline int __attribute__((always_inline))
>     +copy_mbuf_to_desc(struct virtio_net *dev, struct vhost_virtqueue *=
vq,
>     +=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0struct rte_mbuf *m, uint16_t de=
sc_idx, uint32_t *copied)
>     +{
>     ...
>     +=A0 =A0 =A0 =A0while (1) {
>     +=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0/* done with current mbuf, fetch ne=
xt */
>     +=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0if (mbuf_avail =3D=3D 0) {
>     +=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0m =3D m->next;
>     +=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0if (m =3D=3D NULL)
>     +=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0bre=
ak;
>     +
>     +=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0mbuf_offset =3D 0;
>     +=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0mbuf_avail=A0 =3D r=
te_pktmbuf_data_len(m);
>     +=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0}
>     +
>     +=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0/* done with current desc buf, fetc=
h next */
>     +=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0if (desc_avail =3D=3D 0) {
>     +=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0if ((desc->flags & =
VRING_DESC_F_NEXT) =3D=3D 0) {
>     +=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0/* =
Room in vring buffer is not enough */
>     +=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0ret=
urn -1;
>     +=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0}
>     +
>     +=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0desc =3D &vq->desc[=
desc->next];
>     +=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0desc_addr=A0 =A0=3D=
 gpa_to_vva(dev, desc->addr);
>     +=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0desc_offset =3D 0;
>     +=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0desc_avail=A0 =3D d=
esc->len;
>     +=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0}
>     +
>     +=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0COPY(desc_addr + desc_offset,
>     +=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0rte_pktmbuf_mtod_of=
fset(m, uint64_t, mbuf_offset));
>     +=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0PRINT_PACKET(dev, (uintptr_t)(desc_=
addr + desc_offset),
>     +=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 cpy_len, 0=
);
>     +=A0 =A0 =A0 =A0}
>     +=A0 =A0 =A0 =A0*copied =3D rte_pktmbuf_pkt_len(m);
>=20
>=20
> AFAICT m will always be NULL at this point so the call to rte_pktmbuf_l=
en will
> segfault.

Right, I should move it in the beginning of this function.

	--yliu