[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <19129763-6f74-4b04-8a5f-441255b76d34@kernel.org>
Date: Mon, 6 Nov 2023 12:34:52 -0700
From: David Ahern <dsahern@...nel.org>
To: Stanislav Fomichev <sdf@...gle.com>, Mina Almasry <almasrymina@...gle.com>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-arch@...r.kernel.org, linux-kselftest@...r.kernel.org,
linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
linaro-mm-sig@...ts.linaro.org, "David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>, Jesper Dangaard Brouer <hawk@...nel.org>,
Ilias Apalodimas <ilias.apalodimas@...aro.org>, Arnd Bergmann
<arnd@...db.de>, Willem de Bruijn <willemdebruijn.kernel@...il.com>,
Shuah Khan <shuah@...nel.org>, Sumit Semwal <sumit.semwal@...aro.org>,
Christian König <christian.koenig@....com>,
Shakeel Butt <shakeelb@...gle.com>, Jeroen de Borst <jeroendb@...gle.com>,
Praveen Kaligineedi <pkaligineedi@...gle.com>,
Willem de Bruijn <willemb@...gle.com>, Kaiyuan Zhang <kaiyuanz@...gle.com>
Subject: Re: [RFC PATCH v3 09/12] net: add support for skbs with unreadable
frags
On 11/6/23 11:47 AM, Stanislav Fomichev wrote:
> On 11/05, Mina Almasry wrote:
>> For device memory TCP, we expect the skb headers to be available in host
>> memory for access, and we expect the skb frags to be in device memory
>> and unaccessible to the host. We expect there to be no mixing and
>> matching of device memory frags (unaccessible) with host memory frags
>> (accessible) in the same skb.
>>
>> Add a skb->devmem flag which indicates whether the frags in this skb
>> are device memory frags or not.
>>
>> __skb_fill_page_desc() now checks frags added to skbs for page_pool_iovs,
>> and marks the skb as skb->devmem accordingly.
>>
>> Add checks through the network stack to avoid accessing the frags of
>> devmem skbs and avoid coalescing devmem skbs with non devmem skbs.
>>
>> Signed-off-by: Willem de Bruijn <willemb@...gle.com>
>> Signed-off-by: Kaiyuan Zhang <kaiyuanz@...gle.com>
>> Signed-off-by: Mina Almasry <almasrymina@...gle.com>
>>
>> ---
>> include/linux/skbuff.h | 14 +++++++-
>> include/net/tcp.h | 5 +--
>> net/core/datagram.c | 6 ++++
>> net/core/gro.c | 5 ++-
>> net/core/skbuff.c | 77 ++++++++++++++++++++++++++++++++++++------
>> net/ipv4/tcp.c | 6 ++++
>> net/ipv4/tcp_input.c | 13 +++++--
>> net/ipv4/tcp_output.c | 5 ++-
>> net/packet/af_packet.c | 4 +--
>> 9 files changed, 115 insertions(+), 20 deletions(-)
>>
>> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
>> index 1fae276c1353..8fb468ff8115 100644
>> --- a/include/linux/skbuff.h
>> +++ b/include/linux/skbuff.h
>> @@ -805,6 +805,8 @@ typedef unsigned char *sk_buff_data_t;
>> * @csum_level: indicates the number of consecutive checksums found in
>> * the packet minus one that have been verified as
>> * CHECKSUM_UNNECESSARY (max 3)
>> + * @devmem: indicates that all the fragments in this skb are backed by
>> + * device memory.
>> * @dst_pending_confirm: need to confirm neighbour
>> * @decrypted: Decrypted SKB
>> * @slow_gro: state present at GRO time, slower prepare step required
>> @@ -991,7 +993,7 @@ struct sk_buff {
>> #if IS_ENABLED(CONFIG_IP_SCTP)
>> __u8 csum_not_inet:1;
>> #endif
>> -
>> + __u8 devmem:1;
>> #if defined(CONFIG_NET_SCHED) || defined(CONFIG_NET_XGRESS)
>> __u16 tc_index; /* traffic control index */
>> #endif
>> @@ -1766,6 +1768,12 @@ static inline void skb_zcopy_downgrade_managed(struct sk_buff *skb)
>> __skb_zcopy_downgrade_managed(skb);
>> }
>>
>> +/* Return true if frags in this skb are not readable by the host. */
>> +static inline bool skb_frags_not_readable(const struct sk_buff *skb)
>> +{
>> + return skb->devmem;
>
> bikeshedding: should we also rename 'devmem' sk_buff flag to 'not_readable'?
> It better communicates the fact that the stack shouldn't dereference the
> frags (because it has 'devmem' fragments or for some other potential
> future reason).
+1.
Also, the flag on the skb is an optimization - a high level signal that
one or more frags is in unreadable memory. There is no requirement that
all of the frags are in the same memory type.
Powered by blists - more mailing lists