Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753970Ab1ECRgz (ORCPT ); Tue, 3 May 2011 13:36:55 -0400 Received: from e4.ny.us.ibm.com ([32.97.182.144]:56253 "EHLO e4.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753640Ab1ECRgy (ORCPT ); Tue, 3 May 2011 13:36:54 -0400 Subject: Re: [PATCH V3 3/8] Add userspace buffers support in skb From: Shirley Ma To: "Michael S. Tsirkin" Cc: David Miller , Eric Dumazet , Avi Kivity , Arnd Bergmann , netdev@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20110502105348.GA21706@redhat.com> References: <1303328216.19336.18.camel@localhost.localdomain> <1303328877.19336.28.camel@localhost.localdomain> <20110502105348.GA21706@redhat.com> Content-Type: text/plain; charset="UTF-8" Date: Tue, 03 May 2011 10:36:48 -0700 Message-ID: <1304444208.20660.24.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 (2.28.3-1.fc12) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4034 Lines: 112 On Mon, 2011-05-02 at 13:53 +0300, Michael S. Tsirkin wrote: > On Wed, Apr 20, 2011 at 12:47:57PM -0700, Shirley Ma wrote: > > This patch adds userspace buffers support in skb. A new struct > > skb_ubuf_info is needed to maintain the userspace buffers argument > > and index, a callback is used to notify userspace to release the > > buffers once lower device has done DMA (Last reference to that skb > > has gone). > > > > Signed-off-by: Shirley Ma > > --- > > > > include/linux/skbuff.h | 14 ++++++++++++++ > > net/core/skbuff.c | 15 ++++++++++++++- > > 2 files changed, 28 insertions(+), 1 deletions(-) > > > > diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h > > index d0ae90a..47a187b 100644 > > --- a/include/linux/skbuff.h > > +++ b/include/linux/skbuff.h > > @@ -189,6 +189,16 @@ enum { > > SKBTX_DRV_NEEDS_SK_REF = 1 << 3, > > }; > > > > +/* The callback notifies userspace to release buffers when skb DMA > is done in > > + * lower device, the desc is used to track userspace buffer index. > > + */ > > +struct skb_ubuf_info { > > + /* support buffers allocation from userspace */ > > + void (*callback)(struct sk_buff *); > > + void *arg; > > + size_t desc; > > +}; > > + > > /* This data is invariant across clones and lives at > > * the end of the header data, ie. at skb->end. > > */ > > @@ -211,6 +221,10 @@ struct skb_shared_info { > > /* Intermediate layers must ensure that destructor_arg > > * remains valid until skb destructor */ > > void * destructor_arg; > > + > > + /* DMA mapping from/to userspace buffers */ > > + struct skb_ubuf_info ubuf; > > + > > /* must be last field, see pskb_expand_head() */ > > skb_frag_t frags[MAX_SKB_FRAGS]; > > }; > > diff --git a/net/core/skbuff.c b/net/core/skbuff.c > > index 7ebeed0..822c07d 100644 > > --- a/net/core/skbuff.c > > +++ b/net/core/skbuff.c > > @@ -210,6 +210,8 @@ struct sk_buff *__alloc_skb(unsigned int size, > gfp_t gfp_mask, > > shinfo = skb_shinfo(skb); > > memset(shinfo, 0, offsetof(struct skb_shared_info, dataref)); > > atomic_set(&shinfo->dataref, 1); > > + shinfo->ubuf.callback = NULL; > > + shinfo->ubuf.arg = NULL; > > kmemcheck_annotate_variable(shinfo->destructor_arg); > > > > if (fclone) { > > @@ -327,7 +329,15 @@ static void skb_release_data(struct sk_buff > *skb) > > for (i = 0; i < skb_shinfo(skb)->nr_frags; i > ++) > > put_page(skb_shinfo(skb)->frags[i].page); > > } > > - > > + /* > > + * if skb buf is from userspace, we need to notify the > caller > > + * the lower device DMA has done; > > + */ > > + if (skb_shinfo(skb)->ubuf.callback) { > > + skb_shinfo(skb)->ubuf.callback(skb); > > + skb_shinfo(skb)->ubuf.callback = NULL; > > + skb_shinfo(skb)->ubuf.arg = NULL; > > + } > > if (skb_has_frag_list(skb)) > > skb_drop_fraglist(skb); > > > > We probably don't need to touch arg if callback is NULL? Yes. > > @@ -480,6 +490,9 @@ bool skb_recycle_check(struct sk_buff *skb, int > skb_size) > > if (irqs_disabled()) > > return false; > > > > + if (shinfo->ubuf.callback) > > + return false; > > + > > if (skb_is_nonlinear(skb) || skb->fclone != > SKB_FCLONE_UNAVAILABLE) > > return false; > > This is not the only API unsupported for these skbs, is it? > Probably need to check and fail there as well. Yes, I am going through all these skbs to make sure covering all. Thanks Shirley -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/