Re: [PATCH 1/2] iwlwifi: pcie: allow to build an A-MSDU using TSO core

[Emmanuel Grumbach]

Hi Eric,

>
> When the op_mode sends an skb whose payload is bigger than
> MSS, PCIe will create an A-MSDU out of it. PCIe assumes
> that the skb that is coming from the op_mode can fit in one
> A-MSDU. It is the op_mode's responsibility to make sure
> that this guarantee holds.
>
> Additional headers need to be built for the subframes.
> The TSO core code takes care of the IP / TCP headers and
> the driver takes care of the 802.11 subframe headers.
>
> These headers are stored on a per-cpu page that is re-used
> for all the packets handled on that same CPU. Each skb
> holds a reference to that page and releases the page when
> it is reclaimed. When the page gets full, it is released
> and a new one is allocated.
>
> Since any SKB that doesn't go through the fast-xmit path
> of mac80211 will be segmented, we can assume here that the
> packet is not WEP / TKIP and has a proper SNAP header.
>
> Signed-off-by: Emmanuel Grumbach 

Assuming your review queue works as a FIFO and you reviewed the TSO
helper patch, I can assume you ACK this one? :)
Or at least, don't NACK it :)
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[PATCH 1/2] iwlwifi: pcie: allow to build an A-MSDU using TSO core

[Emmanuel Grumbach]

When the op_mode sends an skb whose payload is bigger than
MSS, PCIe will create an A-MSDU out of it. PCIe assumes
that the skb that is coming from the op_mode can fit in one
A-MSDU. It is the op_mode's responsibility to make sure
that this guarantee holds.

Additional headers need to be built for the subframes.
The TSO core code takes care of the IP / TCP headers and
the driver takes care of the 802.11 subframe headers.

These headers are stored on a per-cpu page that is re-used
for all the packets handled on that same CPU. Each skb
holds a reference to that page and releases the page when
it is reclaimed. When the page gets full, it is released
and a new one is allocated.

Since any SKB that doesn't go through the fast-xmit path
of mac80211 will be segmented, we can assume here that the
packet is not WEP / TKIP and has a proper SNAP header.

Signed-off-by: Emmanuel Grumbach 
---
Changes since RFCv4, addressing Eliad's comments:
 * free trans_pcie->tso_hdr_page in the failure path of iwl_trans_pcie_alloc
 * s/alloc_pages(gfp, 0)/alloc_page(gfp)
 * make sure that get_page_hdr's allocation didn't fail
 * use data_left instead of mss for the subframe header's length field
 * free csum_skb in the failure paths
 * identation
---
 drivers/net/wireless/iwlwifi/iwl-devtrace-data.h |  16 ++
 drivers/net/wireless/iwlwifi/iwl-trans.h |   6 +-
 drivers/net/wireless/iwlwifi/pcie/internal.h |   7 +
 drivers/net/wireless/iwlwifi/pcie/trans.c|  16 ++
 drivers/net/wireless/iwlwifi/pcie/tx.c   | 295 ++-
 5 files changed, 334 insertions(+), 6 deletions(-)

diff --git a/drivers/net/wireless/iwlwifi/iwl-devtrace-data.h 
b/drivers/net/wireless/iwlwifi/iwl-devtrace-data.h
index 71a78ce..59d9edf 100644
--- a/drivers/net/wireless/iwlwifi/iwl-devtrace-data.h
+++ b/drivers/net/wireless/iwlwifi/iwl-devtrace-data.h
@@ -51,6 +51,22 @@ TRACE_EVENT(iwlwifi_dev_tx_data,
TP_printk("[%s] TX frame data", __get_str(dev))
 );
 
+TRACE_EVENT(iwlwifi_dev_tx_tso_chunk,
+   TP_PROTO(const struct device *dev,
+u8 *data_src, size_t data_len),
+   TP_ARGS(dev, data_src, data_len),
+   TP_STRUCT__entry(
+   DEV_ENTRY
+
+   __dynamic_array(u8, data, data_len)
+   ),
+   TP_fast_assign(
+   DEV_ASSIGN;
+   memcpy(__get_dynamic_array(data), data_src, data_len);
+   ),
+   TP_printk("[%s] TX frame data", __get_str(dev))
+);
+
 TRACE_EVENT(iwlwifi_dev_rx_data,
TP_PROTO(const struct device *dev,
 const struct iwl_trans *trans,
diff --git a/drivers/net/wireless/iwlwifi/iwl-trans.h 
b/drivers/net/wireless/iwlwifi/iwl-trans.h
index 0ceff69..6919243 100644
--- a/drivers/net/wireless/iwlwifi/iwl-trans.h
+++ b/drivers/net/wireless/iwlwifi/iwl-trans.h
@@ -379,7 +379,11 @@ static inline void iwl_free_rxb(struct iwl_rx_cmd_buffer 
*r)
 }
 
 #define MAX_NO_RECLAIM_CMDS6
-
+/*
+ * The first entry in driver_data array in ieee80211_tx_info
+ * that can be used by the transport.
+ */
+#define IWL_FIRST_DRIVER_DATA 2
 #define IWL_MASK(lo, hi) ((1 << (hi)) | ((1 << (hi)) - (1 << (lo
 
 /*
diff --git a/drivers/net/wireless/iwlwifi/pcie/internal.h 
b/drivers/net/wireless/iwlwifi/pcie/internal.h
index be168d1..7da5643 100644
--- a/drivers/net/wireless/iwlwifi/pcie/internal.h
+++ b/drivers/net/wireless/iwlwifi/pcie/internal.h
@@ -295,6 +295,11 @@ iwl_pcie_get_scratchbuf_dma(struct iwl_txq *txq, int idx)
   sizeof(struct iwl_pcie_txq_scratch_buf) * idx;
 }
 
+struct iwl_tso_hdr_page {
+   struct page *page;
+   u8 *pos;
+};
+
 /**
  * struct iwl_trans_pcie - PCIe transport specific data
  * @rxq: all the RX queue data
@@ -332,6 +337,8 @@ struct iwl_trans_pcie {
struct net_device napi_dev;
struct napi_struct napi;
 
+   struct __percpu iwl_tso_hdr_page *tso_hdr_page;
+
/* INT ICT Table */
__le32 *ict_tbl;
dma_addr_t ict_tbl_dma;
diff --git a/drivers/net/wireless/iwlwifi/pcie/trans.c 
b/drivers/net/wireless/iwlwifi/pcie/trans.c
index a275318..93e488f 100644
--- a/drivers/net/wireless/iwlwifi/pcie/trans.c
+++ b/drivers/net/wireless/iwlwifi/pcie/trans.c
@@ -1601,6 +1601,7 @@ static void iwl_trans_pcie_configure(struct iwl_trans 
*trans,
 void iwl_trans_pcie_free(struct iwl_trans *trans)
 {
struct iwl_trans_pcie *trans_pcie = IWL_TRANS_GET_PCIE_TRANS(trans);
+   int i;
 
 #ifdef CPTCFG_IWLWIFI_PLATFORM_DATA
/* Make sure the device is on before calling pci functions again.
@@ -1631,6 +1632,15 @@ void iwl_trans_pcie_free(struct iwl_trans *trans)
 
iwl_pcie_free_fw_monitor(trans);
 
+   for_each_possible_cpu(i) {
+   struct iwl_tso_hdr_page *p =
+   per_cpu_ptr(trans_pcie->tso_hdr_page, i);
+
+   if (p->page)
+   __free_pages(p->page, 0);
+   }
+
+   free_percpu(trans_pcie->tso_hdr_page);