| Message ID | 461486fac91755ca4e04c2068c102250026dcd0b.1729866134.git.petrm@nvidia.com (mailing list archive) |
|---|---|
| State | New |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | mlxsw: Fixes | expand |
From: Petr Machata <petrm@nvidia.com> Date: Fri, 25 Oct 2024 16:26:26 +0200 > From: Amit Cohen <amcohen@nvidia.com> > > When Rx packet is received, drivers should sync the pages for CPU, to > ensure the CPU reads the data written by the device and not stale > data from its cache. [...] > -static struct sk_buff *mlxsw_pci_rdq_build_skb(struct page *pages[], > +static struct sk_buff *mlxsw_pci_rdq_build_skb(struct mlxsw_pci_queue *q, > + struct page *pages[], > u16 byte_count) > { > + struct mlxsw_pci_queue *cq = q->u.rdq.cq; > unsigned int linear_data_size; > + struct page_pool *page_pool; > struct sk_buff *skb; > int page_index = 0; > bool linear_only; > void *data; > > + linear_only = byte_count + MLXSW_PCI_RX_BUF_SW_OVERHEAD <= PAGE_SIZE; > + linear_data_size = linear_only ? byte_count : > + PAGE_SIZE - > + MLXSW_PCI_RX_BUF_SW_OVERHEAD; Maybe reformat the line while at it? linear_data_size = linear_only ? byte_count : PAGE_SIZE - MLXSW_PCI_RX_BUF_SW_OVERHEAD; > + > + page_pool = cq->u.cq.page_pool; > + page_pool_dma_sync_for_cpu(page_pool, pages[page_index], > + MLXSW_PCI_SKB_HEADROOM, linear_data_size); page_pool_dma_sync_for_cpu() already skips the headroom: dma_sync_single_range_for_cpu(pool->p.dev, offset + pool->p.offset, ... Since your pool->p.offset is MLXSW_PCI_SKB_HEADROOM, I believe you need to pass 0 here. > + > data = page_address(pages[page_index]); > net_prefetch(data); Thanks, Olek
> -----Original Message----- > From: Alexander Lobakin <aleksander.lobakin@intel.com> > Sent: Friday, 25 October 2024 18:00 > To: Petr Machata <petrm@nvidia.com>; Amit Cohen <amcohen@nvidia.com> > Cc: netdev@vger.kernel.org; Andrew Lunn <andrew+netdev@lunn.ch>; David S. Miller <davem@davemloft.net>; Eric Dumazet > <edumazet@google.com>; Jakub Kicinski <kuba@kernel.org>; Paolo Abeni <pabeni@redhat.com>; Simon Horman <horms@kernel.org>; > Danielle Ratson <danieller@nvidia.com>; Ido Schimmel <idosch@nvidia.com>; mlxsw <mlxsw@nvidia.com>; Jiri Pirko <jiri@resnulli.us> > Subject: Re: [PATCH net 2/5] mlxsw: pci: Sync Rx buffers for CPU > > From: Petr Machata <petrm@nvidia.com> > Date: Fri, 25 Oct 2024 16:26:26 +0200 > > > From: Amit Cohen <amcohen@nvidia.com> > > > > When Rx packet is received, drivers should sync the pages for CPU, to > > ensure the CPU reads the data written by the device and not stale > > data from its cache. > > [...] > > > -static struct sk_buff *mlxsw_pci_rdq_build_skb(struct page *pages[], > > +static struct sk_buff *mlxsw_pci_rdq_build_skb(struct mlxsw_pci_queue *q, > > + struct page *pages[], > > u16 byte_count) > > { > > + struct mlxsw_pci_queue *cq = q->u.rdq.cq; > > unsigned int linear_data_size; > > + struct page_pool *page_pool; > > struct sk_buff *skb; > > int page_index = 0; > > bool linear_only; > > void *data; > > > > + linear_only = byte_count + MLXSW_PCI_RX_BUF_SW_OVERHEAD <= PAGE_SIZE; > > + linear_data_size = linear_only ? byte_count : > > + PAGE_SIZE - > > + MLXSW_PCI_RX_BUF_SW_OVERHEAD; > > Maybe reformat the line while at it? > > linear_data_size = linear_only ? byte_count : > PAGE_SIZE - MLXSW_PCI_RX_BUF_SW_OVERHEAD; > > > + > > + page_pool = cq->u.cq.page_pool; > > + page_pool_dma_sync_for_cpu(page_pool, pages[page_index], > > + MLXSW_PCI_SKB_HEADROOM, linear_data_size); > > page_pool_dma_sync_for_cpu() already skips the headroom: > > dma_sync_single_range_for_cpu(pool->p.dev, > offset + pool->p.offset, ... > > Since your pool->p.offset is MLXSW_PCI_SKB_HEADROOM, I believe you need > to pass 0 here. Our pool->p.offset is zero. We use the page pool to allocate buffers for scatter/gather entries. Only the first entry saves headroom for software usage, so only for the first buffer of the packet we pass headroom to page_pool_dma_sync_for_cpu(). > > > + > > data = page_address(pages[page_index]); > > net_prefetch(data); > > Thanks, > Olek
diff --git a/drivers/net/ethernet/mellanox/mlxsw/pci.c b/drivers/net/ethernet/mellanox/mlxsw/pci.c index 060e5b939211..2320a5f323b4 100644 --- a/drivers/net/ethernet/mellanox/mlxsw/pci.c +++ b/drivers/net/ethernet/mellanox/mlxsw/pci.c @@ -389,15 +389,27 @@ static void mlxsw_pci_wqe_frag_unmap(struct mlxsw_pci *mlxsw_pci, char *wqe, dma_unmap_single(&pdev->dev, mapaddr, frag_len, direction); } -static struct sk_buff *mlxsw_pci_rdq_build_skb(struct page *pages[], +static struct sk_buff *mlxsw_pci_rdq_build_skb(struct mlxsw_pci_queue *q, + struct page *pages[], u16 byte_count) { + struct mlxsw_pci_queue *cq = q->u.rdq.cq; unsigned int linear_data_size; + struct page_pool *page_pool; struct sk_buff *skb; int page_index = 0; bool linear_only; void *data; + linear_only = byte_count + MLXSW_PCI_RX_BUF_SW_OVERHEAD <= PAGE_SIZE; + linear_data_size = linear_only ? byte_count : + PAGE_SIZE - + MLXSW_PCI_RX_BUF_SW_OVERHEAD; + + page_pool = cq->u.cq.page_pool; + page_pool_dma_sync_for_cpu(page_pool, pages[page_index], + MLXSW_PCI_SKB_HEADROOM, linear_data_size); + data = page_address(pages[page_index]); net_prefetch(data); @@ -405,11 +417,6 @@ static struct sk_buff *mlxsw_pci_rdq_build_skb(struct page *pages[], if (unlikely(!skb)) return ERR_PTR(-ENOMEM); - linear_only = byte_count + MLXSW_PCI_RX_BUF_SW_OVERHEAD <= PAGE_SIZE; - linear_data_size = linear_only ? byte_count : - PAGE_SIZE - - MLXSW_PCI_RX_BUF_SW_OVERHEAD; - skb_reserve(skb, MLXSW_PCI_SKB_HEADROOM); skb_put(skb, linear_data_size); @@ -425,6 +432,7 @@ static struct sk_buff *mlxsw_pci_rdq_build_skb(struct page *pages[], page = pages[page_index]; frag_size = min(byte_count, PAGE_SIZE); + page_pool_dma_sync_for_cpu(page_pool, page, 0, frag_size); skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags, page, 0, frag_size, PAGE_SIZE); byte_count -= frag_size; @@ -760,7 +768,7 @@ static void mlxsw_pci_cqe_rdq_handle(struct mlxsw_pci *mlxsw_pci, if (err) goto out; - skb = mlxsw_pci_rdq_build_skb(pages, byte_count); + skb = mlxsw_pci_rdq_build_skb(q, pages, byte_count); if (IS_ERR(skb)) { dev_err_ratelimited(&pdev->dev, "Failed to build skb for RDQ\n"); mlxsw_pci_rdq_pages_recycle(q, pages, num_sg_entries);