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SubjectRe: [PATCH net-next v5 4/9] xen-netback: Change RX path for mapped SKB fragments
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On Mon, 2014-01-20 at 21:24 +0000, Zoltan Kiss wrote:

Re the Subject: change how? Perhaps "handle foreign mapped pages on the
guest RX path" would be clearer.

> RX path need to know if the SKB fragments are stored on pages from another
> domain.

Does this not need to be done either before the mapping change or at the
same time? -- otherwise you have a window of a couple of commits where
things are broken, breaking bisectability.

>
> v4:
> - indentation fixes
>
> Signed-off-by: Zoltan Kiss <zoltan.kiss@citrix.com>
> ---
> drivers/net/xen-netback/netback.c | 46 +++++++++++++++++++++++++++++++++----
> 1 file changed, 41 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
> index f74fa92..d43444d 100644
> --- a/drivers/net/xen-netback/netback.c
> +++ b/drivers/net/xen-netback/netback.c
> @@ -226,7 +226,9 @@ static struct xenvif_rx_meta *get_next_rx_buffer(struct xenvif *vif,
> static void xenvif_gop_frag_copy(struct xenvif *vif, struct sk_buff *skb,
> struct netrx_pending_operations *npo,
> struct page *page, unsigned long size,
> - unsigned long offset, int *head)
> + unsigned long offset, int *head,
> + struct xenvif *foreign_vif,
> + grant_ref_t foreign_gref)
> {
> struct gnttab_copy *copy_gop;
> struct xenvif_rx_meta *meta;
> @@ -268,8 +270,15 @@ static void xenvif_gop_frag_copy(struct xenvif *vif, struct sk_buff *skb,
> copy_gop->flags = GNTCOPY_dest_gref;
> copy_gop->len = bytes;
>
> - copy_gop->source.domid = DOMID_SELF;
> - copy_gop->source.u.gmfn = virt_to_mfn(page_address(page));
> + if (foreign_vif) {
> + copy_gop->source.domid = foreign_vif->domid;
> + copy_gop->source.u.ref = foreign_gref;
> + copy_gop->flags |= GNTCOPY_source_gref;
> + } else {
> + copy_gop->source.domid = DOMID_SELF;
> + copy_gop->source.u.gmfn =
> + virt_to_mfn(page_address(page));
> + }
> copy_gop->source.offset = offset;
>
> copy_gop->dest.domid = vif->domid;
> @@ -330,6 +339,9 @@ static int xenvif_gop_skb(struct sk_buff *skb,
> int old_meta_prod;
> int gso_type;
> int gso_size;
> + struct ubuf_info *ubuf = skb_shinfo(skb)->destructor_arg;
> + grant_ref_t foreign_grefs[MAX_SKB_FRAGS];
> + struct xenvif *foreign_vif = NULL;
>
> old_meta_prod = npo->meta_prod;
>
> @@ -370,6 +382,26 @@ static int xenvif_gop_skb(struct sk_buff *skb,
> npo->copy_off = 0;
> npo->copy_gref = req->gref;
>
> + if ((skb_shinfo(skb)->tx_flags & SKBTX_DEV_ZEROCOPY) &&
> + (ubuf->callback == &xenvif_zerocopy_callback)) {
> + u16 pending_idx = ubuf->desc;
> + int i = 0;
> + struct pending_tx_info *temp =
> + container_of(ubuf,
> + struct pending_tx_info,
> + callback_struct);
> + foreign_vif =
> + container_of(temp - pending_idx,
> + struct xenvif,
> + pending_tx_info[0]);
> + do {
> + pending_idx = ubuf->desc;
> + foreign_grefs[i++] =
> + foreign_vif->pending_tx_info[pending_idx].req.gref;
> + ubuf = (struct ubuf_info *) ubuf->ctx;
> + } while (ubuf);
> + }
> +
> data = skb->data;
> while (data < skb_tail_pointer(skb)) {
> unsigned int offset = offset_in_page(data);
> @@ -379,7 +411,9 @@ static int xenvif_gop_skb(struct sk_buff *skb,
> len = skb_tail_pointer(skb) - data;
>
> xenvif_gop_frag_copy(vif, skb, npo,
> - virt_to_page(data), len, offset, &head);
> + virt_to_page(data), len, offset, &head,
> + NULL,
> + 0);
> data += len;
> }
>
> @@ -388,7 +422,9 @@ static int xenvif_gop_skb(struct sk_buff *skb,
> skb_frag_page(&skb_shinfo(skb)->frags[i]),
> skb_frag_size(&skb_shinfo(skb)->frags[i]),
> skb_shinfo(skb)->frags[i].page_offset,
> - &head);
> + &head,
> + foreign_vif,
> + foreign_grefs[i]);
> }
>
> return npo->meta_prod - old_meta_prod;




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