net/mlx5e: XDP, Fix fifo overrun on XDP_REDIRECT

Before this fix, running high rate traffic through XDP_REDIRECT
with multibuf could overrun the fifo used to release the
xdp frames after tx completi

net/mlx5e: XDP, Fix fifo overrun on XDP_REDIRECT

Before this fix, running high rate traffic through XDP_REDIRECT
with multibuf could overrun the fifo used to release the
xdp frames after tx completion. This resulted in corrupted data
being consumed on the free side.

The culplirt was a miscalculation of the fifo size: the maximum ratio
between fifo entries / data segments was incorrect. This ratio serves to
calculate the max fifo size for a full sq where each packet uses the
worst case number of entries in the fifo.

This patch fixes the formula and names the constant. It also makes sure
that future values will use a power of 2 number of entries for the fifo
mask to work.

Signed-off-by: Dragos Tatulea <dtatulea@nvidia.com>
Fixes: 3f734b8c594b ("net/mlx5e: XDP, Use multiple single-entry objects in xdpi_fifo")
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

show more ...

net/mlx5e: XDP, Use multiple single-entry objects in xdpi_fifo

Here we fix the current wi->num_pkts abuse, as it was used to indicate
multiple xdpi entries in the xdpi_fifo.

Instead, reduce mlx5e_x

net/mlx5e: XDP, Use multiple single-entry objects in xdpi_fifo

Here we fix the current wi->num_pkts abuse, as it was used to indicate
multiple xdpi entries in the xdpi_fifo.

Instead, reduce mlx5e_xdp_info to the size of a single field, making it
a union of unions. Per packet, use as many instances as needed to
provide the information needed at the time of completion.

The sequence of xdpi instances pushed is well defined, derived by the
xmit_mode.

Reviewed-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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net/mlx5e: Introduce extended version for mlx5e_xmit_data

Introduce struct mlx5e_xmit_data_frags to be used for non-linear xmit
buffers. Let it include sinfo pointer.

Take one bit from the len fiel

net/mlx5e: Introduce extended version for mlx5e_xmit_data

Introduce struct mlx5e_xmit_data_frags to be used for non-linear xmit
buffers. Let it include sinfo pointer.

Take one bit from the len field to indicate if the descriptor has
fragments and can be casted-up into the extended version.

Zero-init to make sure has_frags, and potentially future fields, are
zero when not explicitly assigned.

Another field will be added in a downstream patch to indicate and point
to dma addresses of the different frags, for redirect-in requests.

This simplifies the mlx5e_xmit_xdp_frame/mlx5e_xmit_xdp_frame_mpwqe
functions params.

Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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net/mlx5e: Move XDP struct and enum to XDP header

Move struct mlx5e_xdp_info and enum mlx5e_xdp_xmit_mode from the generic
en.h to the XDP header, where they belong.

Reviewed-by: Saeed Mahameed <sa

net/mlx5e: Move XDP struct and enum to XDP header

Move struct mlx5e_xdp_info and enum mlx5e_xdp_xmit_mode from the generic
en.h to the XDP header, where they belong.

Reviewed-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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net/mlx5e: Remove redundant page argument in mlx5e_xdp_handle()

Remove the page parameter, it can be derived from the xdp_buff member
of mlx5e_xdp_buff.

Signed-off-by: Tariq Toukan <tariqt@nvidia.c

net/mlx5e: Remove redundant page argument in mlx5e_xdp_handle()

Remove the page parameter, it can be derived from the xdp_buff member
of mlx5e_xdp_buff.

Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Dragos Tatulea <dtatulea@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

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net/mlx5e: Support RX XDP metadata

Support RX hash and timestamp metadata kfuncs. We need to pass in the cqe
pointer to the mlx5e_skb_from* functions so it can be retrieved from the
XDP ctx to do th

net/mlx5e: Support RX XDP metadata

Support RX hash and timestamp metadata kfuncs. We need to pass in the cqe
pointer to the mlx5e_skb_from* functions so it can be retrieved from the
XDP ctx to do this.

Cc: Tariq Toukan <tariqt@nvidia.com>
Cc: Saeed Mahameed <saeedm@nvidia.com>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Martin KaFai Lau <martin.lau@linux.dev>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Willem de Bruijn <willemb@google.com>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Anatoly Burakov <anatoly.burakov@intel.com>
Cc: Alexander Lobakin <alexandr.lobakin@intel.com>
Cc: Magnus Karlsson <magnus.karlsson@gmail.com>
Cc: Maryam Tahhan <mtahhan@redhat.com>
Cc: xdp-hints@xdp-project.net
Cc: netdev@vger.kernel.org
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://lore.kernel.org/r/20230119221536.3349901-17-sdf@google.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>

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net/mlx5e: Introduce wrapper for xdp_buff

Preparation for implementing HW metadata kfuncs. No functional change.

Cc: Tariq Toukan <tariqt@nvidia.com>
Cc: Saeed Mahameed <saeedm@nvidia.com>
Cc: John

net/mlx5e: Introduce wrapper for xdp_buff

Preparation for implementing HW metadata kfuncs. No functional change.

Cc: Tariq Toukan <tariqt@nvidia.com>
Cc: Saeed Mahameed <saeedm@nvidia.com>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Martin KaFai Lau <martin.lau@linux.dev>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Willem de Bruijn <willemb@google.com>
Cc: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Anatoly Burakov <anatoly.burakov@intel.com>
Cc: Alexander Lobakin <alexandr.lobakin@intel.com>
Cc: Magnus Karlsson <magnus.karlsson@gmail.com>
Cc: Maryam Tahhan <mtahhan@redhat.com>
Cc: xdp-hints@xdp-project.net
Cc: netdev@vger.kernel.org
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://lore.kernel.org/r/20230119221536.3349901-16-sdf@google.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>

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net/mlx5e: Fix a typo in mlx5e_xdp_mpwqe_is_full

Fix a typo in the function name: mpqwe -> mpwqe (stands for multi-packet
work queue element).

Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com>

net/mlx5e: Fix a typo in mlx5e_xdp_mpwqe_is_full

Fix a typo in the function name: mpqwe -> mpwqe (stands for multi-packet
work queue element).

Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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net/mlx5e: Remove MLX5E_XDP_TX_DS_COUNT

After introducing multi-buffer XDP_TX, the MLX5E_XDP_TX_DS_COUNT define
became misleading. It's no longer the DS count of an XDP_TX WQE, this
WQE can be longe

net/mlx5e: Remove MLX5E_XDP_TX_DS_COUNT

After introducing multi-buffer XDP_TX, the MLX5E_XDP_TX_DS_COUNT define
became misleading. It's no longer the DS count of an XDP_TX WQE, this
WQE can be longer because of fragments.

As this define is only used at one place in mlx5e_open_xdpsq(), it's
also not very useful anymore. This commit removes the define and puts
the calculation of ds_count for prefilled single-fragment WQEs inline.

Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

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net/mlx5e: Implement sending multi buffer XDP frames

xmit_xdp_frame is extended to support sending fragmented XDP frames. The
next commit will start using this functionality.

Signed-off-by: Maxim M

net/mlx5e: Implement sending multi buffer XDP frames

xmit_xdp_frame is extended to support sending fragmented XDP frames. The
next commit will start using this functionality.

Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

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net/mlx5e: Move mlx5e_xdpi_fifo_push out of xmit_xdp_frame

The implementations of xmit_xdp_frame get the xdpi parameter of type
struct mlx5e_xdp_info for the sole purpose of calling
mlx5e_xdpi_fifo_

net/mlx5e: Move mlx5e_xdpi_fifo_push out of xmit_xdp_frame

The implementations of xmit_xdp_frame get the xdpi parameter of type
struct mlx5e_xdp_info for the sole purpose of calling
mlx5e_xdpi_fifo_push() on success.

This commit moves this call outside of xmit_xdp_frame, shifting this
responsibility to the caller. It will allow more fine-grained handling
of XDP info for cases when an xdp_frame is fragmented.

Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

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net/mlx5e: Store DMA address inside struct page

Use page_pool_set_dma_addr() to store the DMA address of a page inside
struct page, in order to avoid passing struct mlx5e_dma_info to XDP
handlers. P

net/mlx5e: Store DMA address inside struct page

Use page_pool_set_dma_addr() to store the DMA address of a page inside
struct page, in order to avoid passing struct mlx5e_dma_info to XDP
handlers. Previously, struct mlx5e_dma_info was used to pass both the
DMA address and the page, and it worked well for the single-fragment
case.

When XDP multi buffer is in use, and a fragmented xdp_frame has to be
transmitted, the driver needs to know the DMA addresses of fragments,
however, the array of fragments in struct skb_shared_info doesn't
contain them. In order to pass the DMA addresses, the driver puts them
into struct page itself, which is accessible from the array of fragments
in struct skb_shared_info. The existing XDP handlers are modified to
remove the dependency on struct mlx5e_dma_info.

Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

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net/mlx5e: Drop the len output parameter from mlx5e_xdp_handle

The len parameter of mlx5e_xdp_handle is used to output the new packet
length after XDP has processed the packet and returned XDP_PASS.

net/mlx5e: Drop the len output parameter from mlx5e_xdp_handle

The len parameter of mlx5e_xdp_handle is used to output the new packet
length after XDP has processed the packet and returned XDP_PASS.
However, this value can be calculated on the caller site, as the caller
knows if it was an XDP_PASS.

This commit drops the len parameter and moves the calculation to the
caller, reducing the number of parameters passed to the function and
preparing for XDP support in non-linear legacy RQ.

Signed-off-by: Maxim Mikityanskiy <maximmi@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

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net/mlx5e: RX, Test the XDP program existence out of the handler

Instead of early return inside mlx5e_xdp_handle(), let the caller check
if an XDP program is loaded. This allows saving a few unnece

net/mlx5e: RX, Test the XDP program existence out of the handler

Instead of early return inside mlx5e_xdp_handle(), let the caller check
if an XDP program is loaded. This allows saving a few unnecessary
function calls and calculations in case !prog.

Performance test: single core, drop packets in iptables
Before: 3,872,504 pps
After: 3,975,628 pps (+2.66%)

Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Maxim Mikityanskiy <maximmi@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

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net/mlx5e: Use FW limitation for max MPW WQEBBs

Calculate maximal count of MPW WQEBBs on SQ's creation and store it
there. Remove MLX5E_TX_MPW_MAX_NUM_DS and MLX5E_TX_MPW_MAX_WQEBBS.
Update mlx5e_tx

net/mlx5e: Use FW limitation for max MPW WQEBBs

Calculate maximal count of MPW WQEBBs on SQ's creation and store it
there. Remove MLX5E_TX_MPW_MAX_NUM_DS and MLX5E_TX_MPW_MAX_WQEBBS.
Update mlx5e_tx_mpwqe_is_full() and mlx5e_xdp_mpqwe_is_full() .

Signed-off-by: Aya Levin <ayal@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

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net/mlx5e: Replace synchronize_rcu with synchronize_net

The commit cited below switched from using napi_synchronize to
synchronize_rcu to have a guarantee that it will finish in finite time.
However

net/mlx5e: Replace synchronize_rcu with synchronize_net

The commit cited below switched from using napi_synchronize to
synchronize_rcu to have a guarantee that it will finish in finite time.
However, on average, synchronize_rcu takes more time than
napi_synchronize. Given that it's called multiple times per channel on
deactivation, it accumulates to a significant amount, which causes
timeouts in some applications (for example, when using bonding with
NetworkManager).

This commit replaces synchronize_rcu with synchronize_net, which is
faster when called under rtnl_lock, allowing to speed up the described
flow.

Fixes: 9c25a22dfb00 ("net/mlx5e: Use synchronize_rcu to sync with NAPI")
Signed-off-by: Maxim Mikityanskiy <maximmi@mellanox.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

show more ...

net/mlx5e: Replace synchronize_rcu with synchronize_net

[ Upstream commit 4d6e6b0c6d4bed8a7128500701354e2dc6098fa3 ]

The commit cited below switched from using napi_synchronize to
synchronize_rcu t

net/mlx5e: Replace synchronize_rcu with synchronize_net

[ Upstream commit 4d6e6b0c6d4bed8a7128500701354e2dc6098fa3 ]

The commit cited below switched from using napi_synchronize to
synchronize_rcu to have a guarantee that it will finish in finite time.
However, on average, synchronize_rcu takes more time than
napi_synchronize. Given that it's called multiple times per channel on
deactivation, it accumulates to a significant amount, which causes
timeouts in some applications (for example, when using bonding with
NetworkManager).

This commit replaces synchronize_rcu with synchronize_net, which is
faster when called under rtnl_lock, allowing to speed up the described
flow.

Fixes: 9c25a22dfb00 ("net/mlx5e: Use synchronize_rcu to sync with NAPI")
Signed-off-by: Maxim Mikityanskiy <maximmi@mellanox.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

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net/mlx5e: Enhanced TX MPWQE for SKBs

This commit adds support for Enhanced TX MPWQE feature in the regular
(SKB) data path. A MPWQE (multi-packet work queue element) can serve
multiple packets, red

net/mlx5e: Enhanced TX MPWQE for SKBs

This commit adds support for Enhanced TX MPWQE feature in the regular
(SKB) data path. A MPWQE (multi-packet work queue element) can serve
multiple packets, reducing the PCI bandwidth on control traffic.

Two new stats (tx*_mpwqe_blks and tx*_mpwqe_pkts) are added. The feature
is on by default and controlled by the skb_tx_mpwqe private flag.

In a MPWQE, eseg is shared among all packets, so eseg-based offloads
(IPSEC, GENEVE, checksum) run on a separate eseg that is compared to the
eseg of the current MPWQE session to decide if the new packet can be
added to the same session.

MPWQE is not compatible with certain offloads and features, such as TLS
offload, TSO, nonlinear SKBs. If such incompatible features are in use,
the driver gracefully falls back to non-MPWQE.

This change has no performance impact in TCP single stream test and
XDP_TX single stream test.

UDP pktgen, 64-byte packets, single stream, MPWQE off:
Packet rate: 16.96 Mpps (±0.12 Mpps) -> 17.01 Mpps (±0.20 Mpps)
Instructions per packet: 421 -> 429
Cycles per packet: 156 -> 161
Instructions per cycle: 2.70 -> 2.67

UDP pktgen, 64-byte packets, single stream, MPWQE on:
Packet rate: 16.96 Mpps (±0.12 Mpps) -> 20.94 Mpps (±0.33 Mpps)
Instructions per packet: 421 -> 329
Cycles per packet: 156 -> 123
Instructions per cycle: 2.70 -> 2.67

Enabling MPWQE can reduce PCI bandwidth:
PCI Gen2, pktgen at fixed rate of 36864000 pps on 24 CPU cores:
Inbound PCI utilization with MPWQE off: 80.3%
Inbound PCI utilization with MPWQE on: 59.0%
PCI Gen3, pktgen at fixed rate of 56064000 pps on 24 CPU cores:
Inbound PCI utilization with MPWQE off: 65.4%
Inbound PCI utilization with MPWQE on: 49.3%

Enabling MPWQE can also reduce CPU load, increasing the packet rate in
case of CPU bottleneck:
PCI Gen2, pktgen at full rate on 24 CPU cores:
Packet rate with MPWQE off: 37.5 Mpps
Packet rate with MPWQE on: 49.0 Mpps
PCI Gen3, pktgen at full rate on 24 CPU cores:
Packet rate with MPWQE off: 57.0 Mpps
Packet rate with MPWQE on: 66.8 Mpps

Burst size in all pktgen tests is 32.

CPU: Intel(R) Xeon(R) CPU E5-2680 v3 @ 2.50GHz (x86_64)
NIC: Mellanox ConnectX-6 Dx
GCC 10.2.0

Signed-off-by: Maxim Mikityanskiy <maximmi@mellanox.com>
Reviewed-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

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net/mlx5e: Rename xmit-related structs to generalize them

As preparation for the upcoming TX MPWQE support for SKBs, rename struct
mlx5e_xdp_mpwqe to mlx5e_tx_mpwqe and move it above struct mlx5e_tx

net/mlx5e: Rename xmit-related structs to generalize them

As preparation for the upcoming TX MPWQE support for SKBs, rename struct
mlx5e_xdp_mpwqe to mlx5e_tx_mpwqe and move it above struct mlx5e_txqsq.
This structure will be reused in the regular SQ and in the regular TX
data path. Also rename mlx5e_xdp_xmit_data to mlx5e_xmit_data - it will
be used in the upcoming TX MPWQE flow.

Signed-off-by: Maxim Mikityanskiy <maximmi@mellanox.com>
Reviewed-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

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net/mlx5e: Generalize TX MPWQE checks for full session

As preparation for the upcoming TX MPWQE for SKBs, create a function
(mlx5e_tx_mpwqe_is_full) to check whether an MPWQE session is full. This
f

net/mlx5e: Generalize TX MPWQE checks for full session

As preparation for the upcoming TX MPWQE for SKBs, create a function
(mlx5e_tx_mpwqe_is_full) to check whether an MPWQE session is full. This
function will be shared by MPWQE code for XDP and for SKBs. Defines are
renamed and moved to make them not XDP-specific.

Signed-off-by: Maxim Mikityanskiy <maximmi@mellanox.com>
Reviewed-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

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net/mlx5e: Unify constants for WQE_EMPTY_DS_COUNT

A constant for the number of DS in an empty WQE (i.e. a WQE without data
segments) is needed in multiple places (normal TX data path, MPWQE in
XDP),

net/mlx5e: Unify constants for WQE_EMPTY_DS_COUNT

A constant for the number of DS in an empty WQE (i.e. a WQE without data
segments) is needed in multiple places (normal TX data path, MPWQE in
XDP), but currently we have a constant for XDP and an inline formula in
normal TX. This patch introduces a common constant.

Additionally, mlx5e_xdp_mpwqe_session_start is converted to use struct
assignment, because the code nearby is touched.

Signed-off-by: Maxim Mikityanskiy <maximmi@mellanox.com>
Reviewed-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

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net/mlx5e: Small improvements for XDP TX MPWQE logic

Use MLX5E_XDP_MPW_MAX_WQEBBS to reserve space for a MPWQE, because it's
actually the maximal size a MPWQE can take.

Reorganize the logic that ch

net/mlx5e: Small improvements for XDP TX MPWQE logic

Use MLX5E_XDP_MPW_MAX_WQEBBS to reserve space for a MPWQE, because it's
actually the maximal size a MPWQE can take.

Reorganize the logic that checks when to close the MPWQE session:

1. Put all checks into a single function.

2. When inline is on, make only one comparison - if it's false, the less
strict one will also be false. The compiler probably optimized it out
anyway, but it's clearer to also reflect it in the code.

The MLX5E_XDP_INLINE_WQE_* defines are also changed to make the
calculations more correct from the logical point of view. Though
MLX5E_XDP_INLINE_WQE_MAX_DS_CNT used to be 16 and didn't change its
value, the calculation used to be DIV_ROUND_UP(max inline packet size,
MLX5_SEND_WQE_DS), and the numerator should have included sizeof(struct
mlx5_wqe_inline_seg).

Signed-off-by: Maxim Mikityanskiy <maximmi@mellanox.com>
Reviewed-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

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net/mlx5e: XDP, Avoid indirect call in TX flow

Use INDIRECT_CALL_2() helper to avoid the cost of the indirect call
when/if CONFIG_RETPOLINE=y.

Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Revi

net/mlx5e: XDP, Avoid indirect call in TX flow

Use INDIRECT_CALL_2() helper to avoid the cost of the indirect call
when/if CONFIG_RETPOLINE=y.

Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Reviewed-by: Maxim Mikityanskiy <maximmi@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

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mlx5, xsk: Migrate to new MEM_TYPE_XSK_BUFF_POOL

Use the new MEM_TYPE_XSK_BUFF_POOL API in lieu of MEM_TYPE_ZERO_COPY in
mlx5e. It allows to drop a lot of code from the driver (which is now
common i

mlx5, xsk: Migrate to new MEM_TYPE_XSK_BUFF_POOL

Use the new MEM_TYPE_XSK_BUFF_POOL API in lieu of MEM_TYPE_ZERO_COPY in
mlx5e. It allows to drop a lot of code from the driver (which is now
common in AF_XDP core and was related to XSK RX frame allocation, DMA
mapping, etc.) and slightly improve performance (RX +0.8 Mpps, TX +0.4
Mpps).

rfc->v1: Put back the sanity check for XSK params, use XSK API to get
the total headroom size. (Maxim)

v1->v2: Fix DMA address handling, set XDP metadata to invalid. (Maxim)

v2->v3: Handle frame_sz, use xsk_buff_xdp_get_frame_dma, use xsk_buff
API for DMA sync on TX, add performance numbers. (Maxim)

v3->v4: Remove unused variable num_xsk_frames. (Jakub)

Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: Maxim Mikityanskiy <maximmi@mellanox.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200520192103.355233-12-bjorn.topel@gmail.com

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net/mlx5e: Calculate SQ stop room in a robust way

Currently, different formulas are used to estimate the space that may be
taken by WQEs in the SQ during a single packet transmit. This space is
call

net/mlx5e: Calculate SQ stop room in a robust way

Currently, different formulas are used to estimate the space that may be
taken by WQEs in the SQ during a single packet transmit. This space is
called stop room, and it's checked in the end of packet transmit to find
out if the next packet could overflow the SQ. If it could, the driver
tells the kernel to stop sending next packets.

Many factors affect the stop room:

1. Padding with NOPs to avoid WQEs spanning over page boundaries.

2. Enabled and disabled offloads (TLS, upcoming MPWQE).

3. The maximum size of a WQE.

The padding is performed before every WQE if it doesn't fit the current
page.

The current formula assumes that only one padding will be required per
packet, and it doesn't take into account that the WQEs posted during the
transmission of a single packet might exceed the page size in very rare
circumstances. For example, to hit this condition with 4096-byte pages,
TLS offload will have to interrupt an almost-full MPWQE session, be in
the resync flow and try to transmit a near to maximum amount of data.

To avoid SQ overflows in such rare cases after MPWQE is added, this
patch introduces a more robust formula to estimate the stop room. The
new formula uses the fact that a WQE of size X will not require more
than X-1 WQEBBs of padding. More exact estimations are possible, but
they result in much more complex and error-prone code for little gain.

Before this patch, the TLS stop room included space for both INNOVA and
ConnectX TLS offloads that couldn't run at the same time anyway, so this
patch accounts only for the active one.

Signed-off-by: Maxim Mikityanskiy <maximmi@mellanox.com>
Reviewed-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

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