Commit d95f749a authored by Nick Child's avatar Nick Child Committed by Jakub Kicinski
Browse files

ibmvnic: Reduce memcpys in tx descriptor generation 



Previously when creating the header descriptors, the driver would:
1. allocate a temporary buffer on the stack (in build_hdr_descs_arr)
2. memcpy the header info into the temporary buffer (in build_hdr_data)
3. memcpy the temp buffer into a local variable (in create_hdr_descs)
4. copy the local variable into the return buffer (in create_hdr_descs)

Since, there is no opportunity for errors during this process, the temp
buffer is not needed and work can be done on the return buffer directly.

Repurpose build_hdr_data() to only calculate the header lengths. Rename
it to get_hdr_lens().
Edit create_hdr_descs() to read from the skb directly and copy directly
into the returned useful buffer.

The process now involves less memory and write operations while
also being more readable.

Signed-off-by: default avatarNick Child <nnac123@linux.ibm.com>
Link: https://patch.msgid.link/20240807211809.1259563-4-nnac123@linux.ibm.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent b41b45ec

drivers/net/ethernet/ibm/ibmvnic.c

+40 −49
Original line number Diff line number Diff line
@@ -2140,56 +2140,49 @@ static int ibmvnic_close(struct net_device *netdev) 
}



/**

 * build_hdr_data - creates L2/L3/L4 header data buffer

 * get_hdr_lens - fills list of L2/L3/L4 hdr lens

 * @hdr_field: bitfield determining needed headers

 * @skb: socket buffer

 * @hdr_len: array of header lengths

 * @hdr_data: buffer to write the header to

 * @hdr_len: array of header lengths to be filled

 *

 * Reads hdr_field to determine which headers are needed by firmware.

 * Builds a buffer containing these headers.  Saves individual header

 * lengths and total buffer length to be used to build descriptors.

 *

 * Return: total len of all headers

 */

static int build_hdr_data(u8 hdr_field, struct sk_buff *skb,

			  int *hdr_len, u8 *hdr_data)

static int get_hdr_lens(u8 hdr_field, struct sk_buff *skb,

			int *hdr_len)

{

	int len = 0;

	u8 *hdr;





	if (skb->protocol == htons(ETH_P_IP)) {

		if (ip_hdr(skb)->protocol == IPPROTO_TCP)

			hdr_len[2] = tcp_hdrlen(skb);

		else if (ip_hdr(skb)->protocol == IPPROTO_UDP)

			hdr_len[2] = sizeof(struct udphdr);

	} else if (skb->protocol == htons(ETH_P_IPV6)) {

		if (ipv6_hdr(skb)->nexthdr == IPPROTO_TCP)

			hdr_len[2] = tcp_hdrlen(skb);

		else if (ipv6_hdr(skb)->nexthdr == IPPROTO_UDP)

			hdr_len[2] = sizeof(struct udphdr);

	}



	if ((hdr_field >> 6) & 1) {

		hdr_len[0] = skb_mac_header_len(skb);

		hdr = skb_mac_header(skb);

		memcpy(hdr_data, hdr, hdr_len[0]);

		len += hdr_len[0];

	}



	if ((hdr_field >> 5) & 1) {

		hdr_len[1] = skb_network_header_len(skb);

		hdr = skb_network_header(skb);

		memcpy(hdr_data + len, hdr, hdr_len[1]);

		len += hdr_len[1];

	}



	if ((hdr_field >> 4) & 1) {

		hdr = skb_transport_header(skb);

		memcpy(hdr_data + len, hdr, hdr_len[2]);

		len += hdr_len[2];

	if (!((hdr_field >> 4) & 1))

		return len;



	if (skb->protocol == htons(ETH_P_IP)) {

		if (ip_hdr(skb)->protocol == IPPROTO_TCP)

			hdr_len[2] = tcp_hdrlen(skb);

		else if (ip_hdr(skb)->protocol == IPPROTO_UDP)

			hdr_len[2] = sizeof(struct udphdr);

	} else if (skb->protocol == htons(ETH_P_IPV6)) {

		if (ipv6_hdr(skb)->nexthdr == IPPROTO_TCP)

			hdr_len[2] = tcp_hdrlen(skb);

		else if (ipv6_hdr(skb)->nexthdr == IPPROTO_UDP)

			hdr_len[2] = sizeof(struct udphdr);

	}



	return len;

	return len + hdr_len[2];

}



/**
@@ -2202,12 +2195,14 @@ static int build_hdr_data(u8 hdr_field, struct sk_buff *skb, 
 *

 * Creates header and, if needed, header extension descriptors and

 * places them in a descriptor array, scrq_arr

 *

 * Return: Number of header descs

 */



static int create_hdr_descs(u8 hdr_field, u8 *hdr_data, int len, int *hdr_len,

			    union sub_crq *scrq_arr)

{

	union sub_crq hdr_desc;

	union sub_crq *hdr_desc;

	int tmp_len = len;

	int num_descs = 0;

	u8 *data, *cur;
@@ -2216,28 +2211,26 @@ static int create_hdr_descs(u8 hdr_field, u8 *hdr_data, int len, int *hdr_len, 
	while (tmp_len > 0) {

		cur = hdr_data + len - tmp_len;



		memset(&hdr_desc, 0, sizeof(hdr_desc));

		if (cur != hdr_data) {

			data = hdr_desc.hdr_ext.data;

		hdr_desc = &scrq_arr[num_descs];

		if (num_descs) {

			data = hdr_desc->hdr_ext.data;

			tmp = tmp_len > 29 ? 29 : tmp_len;

			hdr_desc.hdr_ext.first = IBMVNIC_CRQ_CMD;

			hdr_desc.hdr_ext.type = IBMVNIC_HDR_EXT_DESC;

			hdr_desc.hdr_ext.len = tmp;

			hdr_desc->hdr_ext.first = IBMVNIC_CRQ_CMD;

			hdr_desc->hdr_ext.type = IBMVNIC_HDR_EXT_DESC;

			hdr_desc->hdr_ext.len = tmp;

		} else {

			data = hdr_desc.hdr.data;

			data = hdr_desc->hdr.data;

			tmp = tmp_len > 24 ? 24 : tmp_len;

			hdr_desc.hdr.first = IBMVNIC_CRQ_CMD;

			hdr_desc.hdr.type = IBMVNIC_HDR_DESC;

			hdr_desc.hdr.len = tmp;

			hdr_desc.hdr.l2_len = (u8)hdr_len[0];

			hdr_desc.hdr.l3_len = cpu_to_be16((u16)hdr_len[1]);

			hdr_desc.hdr.l4_len = (u8)hdr_len[2];

			hdr_desc.hdr.flag = hdr_field << 1;

			hdr_desc->hdr.first = IBMVNIC_CRQ_CMD;

			hdr_desc->hdr.type = IBMVNIC_HDR_DESC;

			hdr_desc->hdr.len = tmp;

			hdr_desc->hdr.l2_len = (u8)hdr_len[0];

			hdr_desc->hdr.l3_len = cpu_to_be16((u16)hdr_len[1]);

			hdr_desc->hdr.l4_len = (u8)hdr_len[2];

			hdr_desc->hdr.flag = hdr_field << 1;

		}

		memcpy(data, cur, tmp);

		tmp_len -= tmp;

		*scrq_arr = hdr_desc;

		scrq_arr++;

		num_descs++;

	}
@@ -2260,13 +2253,11 @@ static void build_hdr_descs_arr(struct sk_buff *skb, 
				int *num_entries, u8 hdr_field)

{

	int hdr_len[3] = {0, 0, 0};

	u8 hdr_data[140] = {0};

	int tot_len;



	tot_len = build_hdr_data(hdr_field, skb, hdr_len,

				 hdr_data);

	*num_entries += create_hdr_descs(hdr_field, hdr_data, tot_len, hdr_len,

					 indir_arr + 1);

	tot_len = get_hdr_lens(hdr_field, skb, hdr_len);

	*num_entries += create_hdr_descs(hdr_field, skb_mac_header(skb),

					 tot_len, hdr_len, indir_arr + 1);

}



static int ibmvnic_xmit_workarounds(struct sk_buff *skb,