Re: [RFC PATCH v1 29/57] net: igb: Remove PAGE_SIZE compile-time constant assumption

Ryan Roberts
2024-10-16T14:54:34Z

+ Alexei Starovoitov, Daniel Borkmann, Jesper Dangaard Brouer, John Fastabend,
Przemek Kitszel, Tony Nguyen

This was a rather tricky series to get the recipients correct for and my script
did not realize that "supporter" was a pseudonym for "maintainer" so you were
missed off the original post. Appologies!

More context in cover letter:
https://lore.kernel.org/all/20241014105514.3206191-1-ryan.roberts@arm.com/

On 14/10/2024 11:58, Ryan Roberts wrote:
> To prepare for supporting boot-time page size selection, refactor code
> to remove assumptions about PAGE_SIZE being compile-time constant. Code
> intended to be equivalent when compile-time page size is active.
>
> Convert CPP conditionals to C conditionals. The compiler will dead code
> strip when doing a compile-time page size build, for the same end
> effect. But this will also work with boot-time page size builds.
>
> Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
> ---
>
> ***NOTE***
> Any confused maintainers may want to read the cover note here for context:
> https://lore.kernel.org/all/20241014105514.3206191-1-ryan.roberts@arm.com/
>
> drivers/net/ethernet/intel/igb/igb.h | 25 ++--
> drivers/net/ethernet/intel/igb/igb_main.c | 149 +++++++++++-----------
> 2 files changed, 82 insertions(+), 92 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/igb/igb.h b/drivers/net/ethernet/intel/igb/igb.h
> index 3c2dc7bdebb50..04aeebcd363b3 100644
> --- a/drivers/net/ethernet/intel/igb/igb.h
> +++ b/drivers/net/ethernet/intel/igb/igb.h
> @@ -158,7 +158,6 @@ struct vf_mac_filter {
> * up negative. In these cases we should fall back to the 3K
> * buffers.
> */
> -#if (PAGE_SIZE < 8192)
> #define IGB_MAX_FRAME_BUILD_SKB (IGB_RXBUFFER_1536 - NET_IP_ALIGN)
> #define IGB_2K_TOO_SMALL_WITH_PADDING \
> ((NET_SKB_PAD + IGB_TS_HDR_LEN + IGB_RXBUFFER_1536) > SKB_WITH_OVERHEAD(IGB_RXBUFFER_2048))
> @@ -177,6 +176,9 @@ static inline int igb_skb_pad(void)
> {
> int rx_buf_len;
>
> + if (PAGE_SIZE >= 8192)
> + return NET_SKB_PAD + NET_IP_ALIGN;
> +
> /* If a 2K buffer cannot handle a standard Ethernet frame then
> * optimize padding for a 3K buffer instead of a 1.5K buffer.
> *
> @@ -196,9 +198,6 @@ static inline int igb_skb_pad(void)
> }
>
> #define IGB_SKB_PAD igb_skb_pad()
> -#else
> -#define IGB_SKB_PAD (NET_SKB_PAD + NET_IP_ALIGN)
> -#endif
>
> /* How many Rx Buffers do we bundle into one write to the hardware ? */
> #define IGB_RX_BUFFER_WRITE 16 /* Must be power of 2 */
> @@ -280,7 +279,7 @@ struct igb_tx_buffer {
> struct igb_rx_buffer {
> dma_addr_t dma;
> struct page *page;
> -#if (BITS_PER_LONG > 32) || (PAGE_SIZE >= 65536)
> +#if (BITS_PER_LONG > 32) || (PAGE_SIZE_MAX >= 65536)
> __u32 page_offset;
> #else
> __u16 page_offset;
> @@ -403,22 +402,20 @@ enum e1000_ring_flags_t {
>
> static inline unsigned int igb_rx_bufsz(struct igb_ring *ring)
> {
> -#if (PAGE_SIZE < 8192)
> - if (ring_uses_large_buffer(ring))
> - return IGB_RXBUFFER_3072;
> + if (PAGE_SIZE < 8192) {
> + if (ring_uses_large_buffer(ring))
> + return IGB_RXBUFFER_3072;
>
> - if (ring_uses_build_skb(ring))
> - return IGB_MAX_FRAME_BUILD_SKB;
> -#endif
> + if (ring_uses_build_skb(ring))
> + return IGB_MAX_FRAME_BUILD_SKB;
> + }
> return IGB_RXBUFFER_2048;
> }
>
> static inline unsigned int igb_rx_pg_order(struct igb_ring *ring)
> {
> -#if (PAGE_SIZE < 8192)
> - if (ring_uses_large_buffer(ring))
> + if (PAGE_SIZE < 8192 && ring_uses_large_buffer(ring))
> return 1;
> -#endif
> return 0;
> }
>
> diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
> index 1ef4cb871452a..4f2c53dece1a2 100644
> --- a/drivers/net/ethernet/intel/igb/igb_main.c
> +++ b/drivers/net/ethernet/intel/igb/igb_main.c
> @@ -4797,9 +4797,7 @@ void igb_configure_rx_ring(struct igb_adapter *adapter,
> static void igb_set_rx_buffer_len(struct igb_adapter *adapter,
> struct igb_ring *rx_ring)
> {
> -#if (PAGE_SIZE < 8192)
> struct e1000_hw *hw = &adapter->hw;
> -#endif
>
> /* set build_skb and buffer size flags */
> clear_ring_build_skb_enabled(rx_ring);
> @@ -4810,12 +4808,11 @@ static void igb_set_rx_buffer_len(struct igb_adapter *adapter,
>
> set_ring_build_skb_enabled(rx_ring);
>
> -#if (PAGE_SIZE < 8192)
> - if (adapter->max_frame_size > IGB_MAX_FRAME_BUILD_SKB ||
> + if (PAGE_SIZE < 8192 &&
> + (adapter->max_frame_size > IGB_MAX_FRAME_BUILD_SKB ||
> IGB_2K_TOO_SMALL_WITH_PADDING ||
> - rd32(E1000_RCTL) & E1000_RCTL_SBP)
> + rd32(E1000_RCTL) & E1000_RCTL_SBP))
> set_ring_uses_large_buffer(rx_ring);
> -#endif
> }
>
> /**
> @@ -5314,12 +5311,10 @@ static void igb_set_rx_mode(struct net_device *netdev)
> E1000_RCTL_VFE);
> wr32(E1000_RCTL, rctl);
>
> -#if (PAGE_SIZE < 8192)
> - if (!adapter->vfs_allocated_count) {
> + if (PAGE_SIZE < 8192 && !adapter->vfs_allocated_count) {
> if (adapter->max_frame_size <= IGB_MAX_FRAME_BUILD_SKB)
> rlpml = IGB_MAX_FRAME_BUILD_SKB;
> }
> -#endif
> wr32(E1000_RLPML, rlpml);
>
> /* In order to support SR-IOV and eventually VMDq it is necessary to set
> @@ -5338,11 +5333,10 @@ static void igb_set_rx_mode(struct net_device *netdev)
>
> /* enable Rx jumbo frames, restrict as needed to support build_skb */
> vmolr &= ~E1000_VMOLR_RLPML_MASK;
> -#if (PAGE_SIZE < 8192)
> - if (adapter->max_frame_size <= IGB_MAX_FRAME_BUILD_SKB)
> + if (PAGE_SIZE < 8192 &&
> + adapter->max_frame_size <= IGB_MAX_FRAME_BUILD_SKB)
> vmolr |= IGB_MAX_FRAME_BUILD_SKB;
> else
> -#endif
> vmolr |= MAX_JUMBO_FRAME_SIZE;
> vmolr |= E1000_VMOLR_LPE;
>
> @@ -8435,17 +8429,17 @@ static bool igb_can_reuse_rx_page(struct igb_rx_buffer *rx_buffer,
> if (!dev_page_is_reusable(page))
> return false;
>
> -#if (PAGE_SIZE < 8192)
> - /* if we are only owner of page we can reuse it */
> - if (unlikely((rx_buf_pgcnt - pagecnt_bias) > 1))
> - return false;
> -#else
> + if (PAGE_SIZE < 8192) {
> + /* if we are only owner of page we can reuse it */
> + if (unlikely((rx_buf_pgcnt - pagecnt_bias) > 1))
> + return false;
> + } else {
> #define IGB_LAST_OFFSET \
> (SKB_WITH_OVERHEAD(PAGE_SIZE) - IGB_RXBUFFER_2048)
>
> - if (rx_buffer->page_offset > IGB_LAST_OFFSET)
> - return false;
> -#endif
> + if (rx_buffer->page_offset > IGB_LAST_OFFSET)
> + return false;
> + }
>
> /* If we have drained the page fragment pool we need to update
> * the pagecnt_bias and page count so that we fully restock the
> @@ -8473,20 +8467,22 @@ static void igb_add_rx_frag(struct igb_ring *rx_ring,
> struct sk_buff *skb,
> unsigned int size)
> {
> -#if (PAGE_SIZE < 8192)
> - unsigned int truesize = igb_rx_pg_size(rx_ring) / 2;
> -#else
> - unsigned int truesize = ring_uses_build_skb(rx_ring) ?
> + unsigned int truesize;
> +
> + if (PAGE_SIZE < 8192)
> + truesize = igb_rx_pg_size(rx_ring) / 2;
> + else
> + truesize = ring_uses_build_skb(rx_ring) ?
> SKB_DATA_ALIGN(IGB_SKB_PAD + size) :
> SKB_DATA_ALIGN(size);
> -#endif
> +
> skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags, rx_buffer->page,
> rx_buffer->page_offset, size, truesize);
> -#if (PAGE_SIZE < 8192)
> - rx_buffer->page_offset ^= truesize;
> -#else
> - rx_buffer->page_offset += truesize;
> -#endif
> +
> + if (PAGE_SIZE < 8192)
> + rx_buffer->page_offset ^= truesize;
> + else
> + rx_buffer->page_offset += truesize;
> }
>
> static struct sk_buff *igb_construct_skb(struct igb_ring *rx_ring,
> @@ -8494,16 +8490,16 @@ static struct sk_buff *igb_construct_skb(struct igb_ring *rx_ring,
> struct xdp_buff *xdp,
> ktime_t timestamp)
> {
> -#if (PAGE_SIZE < 8192)
> - unsigned int truesize = igb_rx_pg_size(rx_ring) / 2;
> -#else
> - unsigned int truesize = SKB_DATA_ALIGN(xdp->data_end -
> - xdp->data_hard_start);
> -#endif
> unsigned int size = xdp->data_end - xdp->data;
> + unsigned int truesize;
> unsigned int headlen;
> struct sk_buff *skb;
>
> + if (PAGE_SIZE < 8192)
> + truesize = igb_rx_pg_size(rx_ring) / 2;
> + else
> + truesize = SKB_DATA_ALIGN(xdp->data_end - xdp->data_hard_start);
> +
> /* prefetch first cache line of first page */
> net_prefetch(xdp->data);
>
> @@ -8529,11 +8525,10 @@ static struct sk_buff *igb_construct_skb(struct igb_ring *rx_ring,
> skb_add_rx_frag(skb, 0, rx_buffer->page,
> (xdp->data + headlen) - page_address(rx_buffer->page),
> size, truesize);
> -#if (PAGE_SIZE < 8192)
> - rx_buffer->page_offset ^= truesize;
> -#else
> - rx_buffer->page_offset += truesize;
> -#endif
> + if (PAGE_SIZE < 8192)
> + rx_buffer->page_offset ^= truesize;
> + else
> + rx_buffer->page_offset += truesize;
> } else {
> rx_buffer->pagecnt_bias++;
> }
> @@ -8546,16 +8541,17 @@ static struct sk_buff *igb_build_skb(struct igb_ring *rx_ring,
> struct xdp_buff *xdp,
> ktime_t timestamp)
> {
> -#if (PAGE_SIZE < 8192)
> - unsigned int truesize = igb_rx_pg_size(rx_ring) / 2;
> -#else
> - unsigned int truesize = SKB_DATA_ALIGN(sizeof(struct skb_shared_info)) +
> - SKB_DATA_ALIGN(xdp->data_end -
> - xdp->data_hard_start);
> -#endif
> unsigned int metasize = xdp->data - xdp->data_meta;
> + unsigned int truesize;
> struct sk_buff *skb;
>
> + if (PAGE_SIZE < 8192)
> + truesize = igb_rx_pg_size(rx_ring) / 2;
> + else
> + truesize = SKB_DATA_ALIGN(sizeof(struct skb_shared_info)) +
> + SKB_DATA_ALIGN(xdp->data_end -
> + xdp->data_hard_start);
> +
> /* prefetch first cache line of first page */
> net_prefetch(xdp->data_meta);
>
> @@ -8575,11 +8571,10 @@ static struct sk_buff *igb_build_skb(struct igb_ring *rx_ring,
> skb_hwtstamps(skb)->hwtstamp = timestamp;
>
> /* update buffer offset */
> -#if (PAGE_SIZE < 8192)
> - rx_buffer->page_offset ^= truesize;
> -#else
> - rx_buffer->page_offset += truesize;
> -#endif
> + if (PAGE_SIZE < 8192)
> + rx_buffer->page_offset ^= truesize;
> + else
> + rx_buffer->page_offset += truesize;
>
> return skb;
> }
> @@ -8634,14 +8629,14 @@ static unsigned int igb_rx_frame_truesize(struct igb_ring *rx_ring,
> {
> unsigned int truesize;
>
> -#if (PAGE_SIZE < 8192)
> - truesize = igb_rx_pg_size(rx_ring) / 2; /* Must be power-of-2 */
> -#else
> - truesize = ring_uses_build_skb(rx_ring) ?
> - SKB_DATA_ALIGN(IGB_SKB_PAD + size) +
> - SKB_DATA_ALIGN(sizeof(struct skb_shared_info)) :
> - SKB_DATA_ALIGN(size);
> -#endif
> + if (PAGE_SIZE < 8192)
> + truesize = igb_rx_pg_size(rx_ring) / 2; /* Must be power-of-2 */
> + else
> + truesize = ring_uses_build_skb(rx_ring) ?
> + SKB_DATA_ALIGN(IGB_SKB_PAD + size) +
> + SKB_DATA_ALIGN(sizeof(struct skb_shared_info)) :
> + SKB_DATA_ALIGN(size);
> +
> return truesize;
> }
>
> @@ -8650,11 +8645,11 @@ static void igb_rx_buffer_flip(struct igb_ring *rx_ring,
> unsigned int size)
> {
> unsigned int truesize = igb_rx_frame_truesize(rx_ring, size);
> -#if (PAGE_SIZE < 8192)
> - rx_buffer->page_offset ^= truesize;
> -#else
> - rx_buffer->page_offset += truesize;
> -#endif
> +
> + if (PAGE_SIZE < 8192)
> + rx_buffer->page_offset ^= truesize;
> + else
> + rx_buffer->page_offset += truesize;
> }
>
> static inline void igb_rx_checksum(struct igb_ring *ring,
> @@ -8825,12 +8820,12 @@ static struct igb_rx_buffer *igb_get_rx_buffer(struct igb_ring *rx_ring,
> struct igb_rx_buffer *rx_buffer;
>
> rx_buffer = &rx_ring->rx_buffer_info[rx_ring->next_to_clean];
> - *rx_buf_pgcnt =
> -#if (PAGE_SIZE < 8192)
> - page_count(rx_buffer->page);
> -#else
> - 0;
> -#endif
> +
> + if (PAGE_SIZE < 8192)
> + *rx_buf_pgcnt = page_count(rx_buffer->page);
> + else
> + *rx_buf_pgcnt = 0;
> +
> prefetchw(rx_buffer->page);
>
> /* we are reusing so sync this buffer for CPU use */
> @@ -8881,9 +8876,8 @@ static int igb_clean_rx_irq(struct igb_q_vector *q_vector, const int budget)
> int rx_buf_pgcnt;
>
> /* Frame size depend on rx_ring setup when PAGE_SIZE=4K */
> -#if (PAGE_SIZE < 8192)
> - frame_sz = igb_rx_frame_truesize(rx_ring, 0);
> -#endif
> + if (PAGE_SIZE < 8192)
> + frame_sz = igb_rx_frame_truesize(rx_ring, 0);
> xdp_init_buff(&xdp, frame_sz, &rx_ring->xdp_rxq);
>
> while (likely(total_packets < budget)) {
> @@ -8932,10 +8926,9 @@ static int igb_clean_rx_irq(struct igb_q_vector *q_vector, const int budget)
>
> xdp_prepare_buff(&xdp, hard_start, offset, size, true);
> xdp_buff_clear_frags_flag(&xdp);
> -#if (PAGE_SIZE > 4096)
> /* At larger PAGE_SIZE, frame_sz depend on len size */
> - xdp.frame_sz = igb_rx_frame_truesize(rx_ring, size);
> -#endif
> + if (PAGE_SIZE > 4096)
> + xdp.frame_sz = igb_rx_frame_truesize(rx_ring, size);
> skb = igb_run_xdp(adapter, rx_ring, &xdp);
> }
>