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[185.107.14.3]) by smtp.gmail.com with ESMTPSA id d7sm10031844wrf.3.2021.09.07.07.31.10 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 07 Sep 2021 07:31:11 -0700 (PDT) From: Jesper Dangaard Brouer X-Google-Original-From: Jesper Dangaard Brouer Cc: brouer@redhat.com, lorenzo.bianconi@redhat.com, davem@davemloft.net, kuba@kernel.org, ast@kernel.org, daniel@iogearbox.net, shayagr@amazon.com, john.fastabend@gmail.com, dsahern@kernel.org, echaudro@redhat.com, jasowang@redhat.com, alexander.duyck@gmail.com, saeed@kernel.org, maciej.fijalkowski@intel.com, magnus.karlsson@intel.com, tirthendu.sarkar@intel.com, toke@redhat.com Subject: Re: [PATCH v13 bpf-next 02/18] xdp: introduce flags field in xdp_buff/xdp_frame To: Lorenzo Bianconi , bpf@vger.kernel.org, netdev@vger.kernel.org References: <980ad3161b9a312510c9fff76fa74e675b8f9bf3.1631007211.git.lorenzo@kernel.org> Message-ID: <52c78ca8-a053-2128-05a0-3aff6f84abd1@redhat.com> Date: Tue, 7 Sep 2021 16:31:10 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <980ad3161b9a312510c9fff76fa74e675b8f9bf3.1631007211.git.lorenzo@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org (Minor changes requested below) On 07/09/2021 14.35, Lorenzo Bianconi wrote: > Introduce flags field in xdp_frame and xdp_buffer data structures > to define additional buffer features. At the moment the only > supported buffer feature is multi-buffer bit (mb). Multi-buffer bit > is used to specify if this is a linear buffer (mb = 0) or a multi-buffer > frame (mb = 1). In the latter case the driver is expected to initialize > the skb_shared_info structure at the end of the first buffer to link > together subsequent buffers belonging to the same frame. > > Acked-by: John Fastabend > Signed-off-by: Lorenzo Bianconi > --- > include/net/xdp.h | 29 +++++++++++++++++++++++++++++ > 1 file changed, 29 insertions(+) > > diff --git a/include/net/xdp.h b/include/net/xdp.h > index ad5b02dcb6f4..ed5ea784fd45 100644 > --- a/include/net/xdp.h > +++ b/include/net/xdp.h > @@ -66,6 +66,10 @@ struct xdp_txq_info { > struct net_device *dev; > }; > > +enum xdp_buff_flags { > + XDP_FLAGS_MULTI_BUFF = BIT(0), /* non-linear xdp buff */ > +}; > + > struct xdp_buff { > void *data; > void *data_end; > @@ -74,13 +78,30 @@ struct xdp_buff { > struct xdp_rxq_info *rxq; > struct xdp_txq_info *txq; > u32 frame_sz; /* frame size to deduce data_hard_end/reserved tailroom*/ > + u16 flags; /* supported values defined in xdp_flags */ ^^^^^^^^^ Variable/enum is named "xdp_buff_flags", but comment says "xdp_flags". I think we should change flags to use u32, because xdp_buff already contain 4 byte padding. (pahole output provided as help below) > }; > > +static __always_inline bool xdp_buff_is_mb(struct xdp_buff *xdp) > +{ > + return !!(xdp->flags & XDP_FLAGS_MULTI_BUFF); > +} > + > +static __always_inline void xdp_buff_set_mb(struct xdp_buff *xdp) > +{ > + xdp->flags |= XDP_FLAGS_MULTI_BUFF; > +} > + > +static __always_inline void xdp_buff_clear_mb(struct xdp_buff *xdp) > +{ > + xdp->flags &= ~XDP_FLAGS_MULTI_BUFF; > +} > + > static __always_inline void > xdp_init_buff(struct xdp_buff *xdp, u32 frame_sz, struct xdp_rxq_info *rxq) > { > xdp->frame_sz = frame_sz; > xdp->rxq = rxq; > + xdp->flags = 0; > } > > static __always_inline void > @@ -122,8 +143,14 @@ struct xdp_frame { > */ > struct xdp_mem_info mem; > struct net_device *dev_rx; /* used by cpumap */ > + u16 flags; /* supported values defined in xdp_flags */ ^^^^^^^^^ Variable/enum is named "xdp_buff_flags", but comment says "xdp_flags". Here (for xdp_frame) I also think we should change flags to u32, because adding this u16 cause extra padding anyhow. (pahole output provided as help below). > }; > > +static __always_inline bool xdp_frame_is_mb(struct xdp_frame *frame) > +{ > + return !!(frame->flags & XDP_FLAGS_MULTI_BUFF); > +} > + > #define XDP_BULK_QUEUE_SIZE 16 > struct xdp_frame_bulk { > int count; > @@ -180,6 +207,7 @@ void xdp_convert_frame_to_buff(struct xdp_frame *frame, struct xdp_buff *xdp) > xdp->data_end = frame->data + frame->len; > xdp->data_meta = frame->data - frame->metasize; > xdp->frame_sz = frame->frame_sz; > + xdp->flags = frame->flags; > } > > static inline > @@ -206,6 +234,7 @@ int xdp_update_frame_from_buff(struct xdp_buff *xdp, > xdp_frame->headroom = headroom - sizeof(*xdp_frame); > xdp_frame->metasize = metasize; > xdp_frame->frame_sz = xdp->frame_sz; > + xdp_frame->flags = xdp->flags; > > return 0; > } > Details below... no need to read any further Investigating struct xdp_frame with pahole: $ pahole -C xdp_frame net/core/xdp.o struct xdp_frame { void * data; /* 0 8 */ u16 len; /* 8 2 */ u16 headroom; /* 10 2 */ u32 metasize:8; /* 12: 0 4 */ u32 frame_sz:24; /* 12: 8 4 */ struct xdp_mem_info mem; /* 16 8 */ struct net_device * dev_rx; /* 24 8 */ /* size: 32, cachelines: 1, members: 7 */ /* last cacheline: 32 bytes */ }; pahole -C xdp_frame net/core/xdp.o struct xdp_frame { void * data; /* 0 8 */ u16 len; /* 8 2 */ u16 headroom; /* 10 2 */ u32 metasize:8; /* 12: 0 4 */ u32 frame_sz:24; /* 12: 8 4 */ struct xdp_mem_info mem; /* 16 8 */ struct net_device * dev_rx; /* 24 8 */ u16 flags; /* 32 2 */ /* size: 40, cachelines: 1, members: 8 */ /* padding: 6 */ /* last cacheline: 40 bytes */ }; $ pahole -C xdp_frame net/core/xdp.o struct xdp_frame { void * data; /* 0 8 */ u16 len; /* 8 2 */ u16 headroom; /* 10 2 */ u32 metasize:8; /* 12: 0 4 */ u32 frame_sz:24; /* 12: 8 4 */ struct xdp_mem_info mem; /* 16 8 */ struct net_device * dev_rx; /* 24 8 */ u32 flags; /* 32 4 */ /* size: 40, cachelines: 1, members: 8 */ /* padding: 4 */ /* last cacheline: 40 bytes */ }; Details for struct xdp_buff, it already contains 4 bytes padding. $ pahole -C xdp_buff net/core/xdp.o struct xdp_buff { void * data; /* 0 8 */ void * data_end; /* 8 8 */ void * data_meta; /* 16 8 */ void * data_hard_start; /* 24 8 */ struct xdp_rxq_info * rxq; /* 32 8 */ struct xdp_txq_info * txq; /* 40 8 */ u32 frame_sz; /* 48 4 */ u16 flags; /* 52 2 */ /* size: 56, cachelines: 1, members: 8 */ /* padding: 2 */ /* last cacheline: 56 bytes */ };