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[73.185.129.58]) by smtp.googlemail.com with ESMTPSA id k14sm1725564iob.34.2021.03.05.12.48.05 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 05 Mar 2021 12:48:06 -0800 (PST) Subject: Re: [PATCH net-next 6/6] net: qualcomm: rmnet: don't use C bit-fields in rmnet checksum header To: Bjorn Andersson Cc: subashab@codeaurora.org, stranche@codeaurora.org, davem@davemloft.net, kuba@kernel.org, sharathv@codeaurora.org, evgreen@chromium.org, cpratapa@codeaurora.org, elder@kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <20210304223431.15045-1-elder@linaro.org> <20210304223431.15045-7-elder@linaro.org> From: Alex Elder Message-ID: <59b7dd84-5115-81e1-f4a4-5cab6466544f@linaro.org> Date: Fri, 5 Mar 2021 14:48:05 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/4/21 11:26 PM, Bjorn Andersson wrote: > On Thu 04 Mar 16:34 CST 2021, Alex Elder wrote: > >> Replace the use of C bit-fields in the rmnet_map_ul_csum_header >> structure with a single two-byte (big endian) structure member, >> and use field masks to encode or get values within it. >> >> Previously rmnet_map_ipv4_ul_csum_header() would update values in >> the host byte-order fields, and then forcibly fix their byte order >> using a combination of byte order operations and types. >> >> Instead, just compute the value that needs to go into the new >> structure member and save it with a simple byte-order conversion. >> >> Make similar simplifications in rmnet_map_ipv6_ul_csum_header(). >> >> Finally, in rmnet_map_checksum_uplink_packet() a set of assignments >> zeroes every field in the upload checksum header. Replace that with >> a single memset() operation. >> >> Signed-off-by: Alex Elder >> --- >> .../ethernet/qualcomm/rmnet/rmnet_map_data.c | 34 ++++++------------- >> include/linux/if_rmnet.h | 21 ++++++------ >> 2 files changed, 21 insertions(+), 34 deletions(-) >> >> diff --git a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c >> index 29d485b868a65..db76bbf000aa1 100644 >> --- a/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c >> +++ b/drivers/net/ethernet/qualcomm/rmnet/rmnet_map_data.c >> @@ -198,23 +198,19 @@ rmnet_map_ipv4_ul_csum_header(void *iphdr, >> struct rmnet_map_ul_csum_header *ul_header, >> struct sk_buff *skb) >> { >> - __be16 *hdr = (__be16 *)ul_header; >> struct iphdr *ip4h = iphdr; >> u16 offset; >> + u16 val; >> >> offset = skb_transport_header(skb) - (unsigned char *)iphdr; >> ul_header->csum_start_offset = htons(offset); >> >> - ul_header->csum_insert_offset = skb->csum_offset; >> - ul_header->csum_enabled = 1; >> + val = be16_encode_bits(1, MAP_CSUM_UL_ENABLED_FMASK); > > Why are you using be16_ here? Won't that cancel the htons() below? Yes. This was a mistake, and as you know, the kernel test robot caught the problem with assigning a big endian value to a host byte order variable. This cannot have worked before and I'm not sure what happened. I've updated this series and am re-testing everything. That includes running the patches through sparse, but also includes running with checksum offload enabled and verifying errors are not reported when checksum offload active. -Alex > Regards, > Bjorn > >> if (ip4h->protocol == IPPROTO_UDP) >> - ul_header->udp_ind = 1; >> - else >> - ul_header->udp_ind = 0; >> + val |= be16_encode_bits(1, MAP_CSUM_UL_UDP_FMASK); >> + val |= be16_encode_bits(skb->csum_offset, MAP_CSUM_UL_OFFSET_FMASK); >> >> - /* Changing remaining fields to network order */ >> - hdr++; >> - *hdr = htons((__force u16)*hdr); >> + ul_header->csum_info = htons(val); >> >> skb->ip_summed = CHECKSUM_NONE; >> >> @@ -241,24 +237,19 @@ rmnet_map_ipv6_ul_csum_header(void *ip6hdr, >> struct rmnet_map_ul_csum_header *ul_header, >> struct sk_buff *skb) >> { >> - __be16 *hdr = (__be16 *)ul_header; >> struct ipv6hdr *ip6h = ip6hdr; >> u16 offset; >> + u16 val; >> >> offset = skb_transport_header(skb) - (unsigned char *)ip6hdr; >> ul_header->csum_start_offset = htons(offset); >> >> - ul_header->csum_insert_offset = skb->csum_offset; >> - ul_header->csum_enabled = 1; >> - >> + val = be16_encode_bits(1, MAP_CSUM_UL_ENABLED_FMASK); >> if (ip6h->nexthdr == IPPROTO_UDP) >> - ul_header->udp_ind = 1; >> - else >> - ul_header->udp_ind = 0; >> + val |= be16_encode_bits(1, MAP_CSUM_UL_UDP_FMASK); >> + val |= be16_encode_bits(skb->csum_offset, MAP_CSUM_UL_OFFSET_FMASK); >> >> - /* Changing remaining fields to network order */ >> - hdr++; >> - *hdr = htons((__force u16)*hdr); >> + ul_header->csum_info = htons(val); >> >> skb->ip_summed = CHECKSUM_NONE; >> >> @@ -425,10 +416,7 @@ void rmnet_map_checksum_uplink_packet(struct sk_buff *skb, >> } >> >> sw_csum: >> - ul_header->csum_start_offset = 0; >> - ul_header->csum_insert_offset = 0; >> - ul_header->csum_enabled = 0; >> - ul_header->udp_ind = 0; >> + memset(ul_header, 0, sizeof(*ul_header)); >> >> priv->stats.csum_sw++; >> } >> diff --git a/include/linux/if_rmnet.h b/include/linux/if_rmnet.h >> index 1fbb7531238b6..149d696feb520 100644 >> --- a/include/linux/if_rmnet.h >> +++ b/include/linux/if_rmnet.h >> @@ -33,17 +33,16 @@ struct rmnet_map_dl_csum_trailer { >> >> struct rmnet_map_ul_csum_header { >> __be16 csum_start_offset; >> -#if defined(__LITTLE_ENDIAN_BITFIELD) >> - u16 csum_insert_offset:14; >> - u16 udp_ind:1; >> - u16 csum_enabled:1; >> -#elif defined (__BIG_ENDIAN_BITFIELD) >> - u16 csum_enabled:1; >> - u16 udp_ind:1; >> - u16 csum_insert_offset:14; >> -#else >> -#error "Please fix " >> -#endif >> + __be16 csum_info; /* MAP_CSUM_UL_*_FMASK */ >> } __aligned(1); >> >> +/* csum_info field: >> + * ENABLED: 1 = checksum computation requested >> + * UDP: 1 = UDP checksum (zero checkum means no checksum) >> + * OFFSET: where (offset in bytes) to insert computed checksum >> + */ >> +#define MAP_CSUM_UL_OFFSET_FMASK GENMASK(13, 0) >> +#define MAP_CSUM_UL_UDP_FMASK GENMASK(14, 14) >> +#define MAP_CSUM_UL_ENABLED_FMASK GENMASK(15, 15) >> + >> #endif /* !(_LINUX_IF_RMNET_H_) */ >> -- >> 2.20.1 >>