net: mana: add ethtool private flag for full-page RX buffers
Subsystems (6)
v13 cover net: mana: add ethtool private flag for full-page RX buffers
On some ARM64 platforms with 4K PAGE_SIZE, utilizing page_pool fragments for allocation in the RX refill path (~2kB buffer per fragment) causes 15-20% throughput regression under high connection counts (>16 TCP streams at 180+ Gbps). Using full-page buffers on these platforms shows no regression and restores line-rate performance.
This behavior is observed on a single platform; other platforms perform better with page_pool fragments, indicating this is not a page_pool issue but platform-specific.
This series adds an ethtool private flag "full-page-rx" to let the user opt in to one RX buffer per page:
ethtool --set-priv-flags eth0 full-page-rx on
There is no behavioral change by default. The flag can be persisted via udev rule for affected platforms.
This series depends on the following fixes now merged in net-next:
commit 17bfe0a8c014 ("net: mana: Add NULL guards in teardown path to prevent panic on attach failure") commit 5b05aa36ee24 ("net: mana: Skip redundant detach on already-detached port")
Changes in v13:
- Dropped patches 2/4 (mana_detach dealloc bail-out fix) and 4/4 (attach failure recovery). Both will be sent as separate series:
the dealloc fix as a standalone fix, and the recovery mechanism after concluding pre-allocate-and-replace approach discussion with the HW team.
- Removed schedule_port_reset logic from mana_set_priv_flags(); on mana_attach() failure, the old priv_flags are restored and the error is returned without scheduling async recovery.
Changes in v12:
- Added patch 2 to ensure mana_detach() always completes its full teardown even if mana_dealloc_queues() fails, keeping port state consistent for recovery.
- Added patch 4 to schedule queue_reset_work when mana_attach() fails during ethtool ring size or channel count changes, with fallback values that maximize recovery chances.
Changes in v11:
- Rebased on net-next
Changes in v10:
- Rebased on net-next which now includes the prerequisite fixes.
- Recovery logic in mana_set_priv_flags() leverages the idempotent mana_detach() from the merged fixes.
Changes in v9:
- Added correct tree.
Changes in v8:
- Fixed queue_reset_work recovery by restoring port_is_up before scheduling reset so the handler can properly re-attach.
- Simplified "err && schedule_port_reset" to "schedule_port_reset".
Changes in v7:
- Rebased onto net-next.
- Retained private flag approach after David Wei's testing on Grace (ARM64) confirmed that fragment mode outperforms full-page mode on other platforms, validating this is a single-platform workaround rather than a generic issue.
Changes in v6:
- Added missed maintainers.
Changes in v5:
- Split prep refactor into separate patch (patch 1/2)
Changes in v4:
- Dropping the smbios string parsing and add ethtool priv flag to reconfigure the queues with full page rx buffers.
Changes in v3:
- changed u8* to char*
Changes in v2:
- separate reading string index and the string, remove inline.
Dipayaan Roy (2):
net: mana: refactor mana_get_strings() and mana_get_sset_count() to
use switch
net: mana: force full-page RX buffers via ethtool private flag
drivers/net/ethernet/microsoft/mana/mana_en.c | 22 ++- .../ethernet/microsoft/mana/mana_ethtool.c | 169 +++++++++++++++--- include/net/mana/mana.h | 8 + 3 files changed, 168 insertions(+), 31 deletions(-)
Signature · 1 line
2.43.0
PATCH v13 1/2 net: mana: refactor mana_get_strings() and mana_get_sset_count() to use switch
Refactor mana_get_strings() and mana_get_sset_count() from if/else to switch statements in preparation for adding ethtool private flags support which requires handling ETH_SS_PRIV_FLAGS.
No functional change.
--- .../ethernet/microsoft/mana/mana_ethtool.c | 75 ++++++++++++------- 1 file changed, 46 insertions(+), 29 deletions(-)
drivers/net/ethernet/microsoft/mana/mana_ethtool.c +46 -29
@@ -138,53 +138,70 @@ static int mana_get_sset_count(struct net_device *ndev, int stringset)struct mana_port_context *apc =netdev_priv (ndev);unsigned int num_queues = apc->num_queues; -if (stringset !=ETH_SS_STATS ) +switch (stringset) { +case ETH_SS_STATS : +return ARRAY_SIZE (mana_eth_stats) + +ARRAY_SIZE (mana_phy_stats) + +ARRAY_SIZE (mana_hc_stats) + + num_queues * (MANA_STATS_RX_COUNT +MANA_STATS_TX_COUNT ); +default :return -EINVAL ; - -return ARRAY_SIZE (mana_eth_stats) +ARRAY_SIZE (mana_phy_stats) +ARRAY_SIZE (mana_hc_stats) + - num_queues * (MANA_STATS_RX_COUNT +MANA_STATS_TX_COUNT ); + } } -static void mana_get_strings (struct net_device *ndev,u32 stringset,u8 *data) +static void mana_get_strings_stats (struct mana_port_context *apc,u8 **data) { -struct mana_port_context *apc =netdev_priv (ndev);unsigned int num_queues = apc->num_queues;int i, j; -if (stringset !=ETH_SS_STATS ) -return ;for (i =0 ; i <ARRAY_SIZE (mana_eth_stats); i++) -ethtool_puts (&data, mana_eth_stats[i].name); +ethtool_puts (data, mana_eth_stats[i].name);for (i =0 ; i <ARRAY_SIZE (mana_hc_stats); i++) -ethtool_puts (&data, mana_hc_stats[i].name); +ethtool_puts (data, mana_hc_stats[i].name);for (i =0 ; i <ARRAY_SIZE (mana_phy_stats); i++) -ethtool_puts (&data, mana_phy_stats[i].name); +ethtool_puts (data, mana_phy_stats[i].name);for (i =0 ; i < num_queues; i++) { -ethtool_sprintf (&data,"rx_%d_packets" , i); -ethtool_sprintf (&data,"rx_%d_bytes" , i); -ethtool_sprintf (&data,"rx_%d_xdp_drop" , i); -ethtool_sprintf (&data,"rx_%d_xdp_tx" , i); -ethtool_sprintf (&data,"rx_%d_xdp_redirect" , i); -ethtool_sprintf (&data,"rx_%d_pkt_len0_err" , i); +ethtool_sprintf (data,"rx_%d_packets" , i); +ethtool_sprintf (data,"rx_%d_bytes" , i); +ethtool_sprintf (data,"rx_%d_xdp_drop" , i); +ethtool_sprintf (data,"rx_%d_xdp_tx" , i); +ethtool_sprintf (data,"rx_%d_xdp_redirect" , i); +ethtool_sprintf (data,"rx_%d_pkt_len0_err" , i);for (j =0 ; j <MANA_RXCOMP_OOB_NUM_PPI -1 ; j++) -ethtool_sprintf (&data,"rx_%d_coalesced_cqe_%d" , i, j +2 ); +ethtool_sprintf (data, +"rx_%d_coalesced_cqe_%d" , + i, + j +2 ); }for (i =0 ; i < num_queues; i++) { -ethtool_sprintf (&data,"tx_%d_packets" , i); -ethtool_sprintf (&data,"tx_%d_bytes" , i); -ethtool_sprintf (&data,"tx_%d_xdp_xmit" , i); -ethtool_sprintf (&data,"tx_%d_tso_packets" , i); -ethtool_sprintf (&data,"tx_%d_tso_bytes" , i); -ethtool_sprintf (&data,"tx_%d_tso_inner_packets" , i); -ethtool_sprintf (&data,"tx_%d_tso_inner_bytes" , i); -ethtool_sprintf (&data,"tx_%d_long_pkt_fmt" , i); -ethtool_sprintf (&data,"tx_%d_short_pkt_fmt" , i); -ethtool_sprintf (&data,"tx_%d_csum_partial" , i); -ethtool_sprintf (&data,"tx_%d_mana_map_err" , i); +ethtool_sprintf (data,"tx_%d_packets" , i); +ethtool_sprintf (data,"tx_%d_bytes" , i); +ethtool_sprintf (data,"tx_%d_xdp_xmit" , i); +ethtool_sprintf (data,"tx_%d_tso_packets" , i); +ethtool_sprintf (data,"tx_%d_tso_bytes" , i); +ethtool_sprintf (data,"tx_%d_tso_inner_packets" , i); +ethtool_sprintf (data,"tx_%d_tso_inner_bytes" , i); +ethtool_sprintf (data,"tx_%d_long_pkt_fmt" , i); +ethtool_sprintf (data,"tx_%d_short_pkt_fmt" , i); +ethtool_sprintf (data,"tx_%d_csum_partial" , i); +ethtool_sprintf (data,"tx_%d_mana_map_err" , i); + } +} + +static void mana_get_strings (struct net_device *ndev,u32 stringset,u8 *data) +{ +struct mana_port_context *apc =netdev_priv (ndev); + +switch (stringset) { +case ETH_SS_STATS : +mana_get_strings_stats (apc, &data); +break ; +default : +break ; } }
Signature · 1 line
2.43.0
PATCH v13 2/2 net: mana: force full-page RX buffers via ethtool private flag
In reply to Dipayaan RoyOn some ARM64 platforms with 4K PAGE_SIZE, page_pool fragment allocation in the RX refill path can cause 15-20% throughput regression under high connection counts (>16 TCP streams).
Add an ethtool private flag "full-page-rx" that allows the user to force one RX buffer per page, bypassing the page_pool fragment path. This restores line-rate (180+ Gbps) performance on affected platforms.
Usage:
ethtool --set-priv-flags eth0 full-page-rx on
There is no behavioral change by default. The flag must be explicitly enabled by the user or udev rule.
The existing single-buffer-per-page logic for XDP and jumbo frames is consolidated into a new helper mana_use_single_rxbuf_per_page() which is now the single decision point for both the automatic and user-controlled paths.
--- drivers/net/ethernet/microsoft/mana/mana_en.c | 22 ++++- .../ethernet/microsoft/mana/mana_ethtool.c | 94 +++++++++++++++++++ include/net/mana/mana.h | 8 ++ 3 files changed, 122 insertions(+), 2 deletions(-)
drivers/net/ethernet/microsoft/mana/mana_en.c +20 -2
@@ -755,6 +755,25 @@ static void *mana_get_rxbuf_pre(struct mana_rxq *rxq, dma_addr_t *da)return va; } +static bool +mana_use_single_rxbuf_per_page (struct mana_port_context *apc,u32 mtu) +{ +/* On some platforms with 4K PAGE_SIZE, page_pool fragment allocation +* in the RX refill path (~2kB buffer) can cause significant throughput +* regression under high connection counts. Allow user to force one RX +* buffer per page via ethtool private flag to bypass the fragment +* path. +*/ +if (apc->priv_flags &BIT (MANA_PRIV_FLAG_USE_FULL_PAGE_RXBUF )) +return true; + +/* For xdp and jumbo frames make sure only one packet fits per page. */ +if (mtu +MANA_RXBUF_PAD >PAGE_SIZE /2 ||mana_xdp_get (apc)) +return true; + +return false; +} +/* Get RX buffer's data size, alloc size, XDP headroom based on MTU */ static void mana_get_rxbuf_cfg(struct mana_port_context *apc, int mtu, u32 *datasize, u32 *alloc_size,
@@ -765,8 +784,7 @@ static void mana_get_rxbuf_cfg(struct mana_port_context *apc,/* Calculate datasize first (consistent across all cases) */ *datasize = mtu +ETH_HLEN ; -/* For xdp and jumbo frames make sure only one packet fits per page */ -if (mtu +MANA_RXBUF_PAD >PAGE_SIZE /2 ||mana_xdp_get (apc)) { +if (mana_use_single_rxbuf_per_page (apc, mtu)) {if (mana_xdp_get (apc)) { *headroom =XDP_PACKET_HEADROOM ; *alloc_size =PAGE_SIZE ;
drivers/net/ethernet/microsoft/mana/mana_ethtool.c +94 -0
134 lines not on this page · raw message
include/net/mana/mana.h +8 -0
@@ -31,6 +31,12 @@ enum TRI_STATE { TRI_STATE_TRUE = 1 }; +/* MANA ethtool private flag bit positions */ +enum mana_priv_flag_bits { +MANA_PRIV_FLAG_USE_FULL_PAGE_RXBUF =0 , +MANA_PRIV_FLAG_MAX , +}; +/* Number of entries for hardware indirection table must be in power of 2 */ #define MANA_INDIRECT_TABLE_MAX_SIZE 512#define MANA_INDIRECT_TABLE_DEF_SIZE 64
@@ -565,6 +571,8 @@ struct mana_port_context {u32 rxbpre_headroom;u32 rxbpre_frag_count; +u32 priv_flags; +struct bpf_prog *bpf_prog;/* Create num_queues EQs, SQs, SQ-CQs, RQs and RQ-CQs, respectively. */
Signature · 1 line
2.43.0
[email protected]
AI reviewRe: [PATCH net-next v13 2/2] net: mana: force full-page RX buffers via ethtool private flag
Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
Pre-existing issues:
- [High] Use-after-free of BPF program when mana_pre_alloc_rxbufs fails during XDP setup --
--- Patch [2]: [PATCH net-next v13 2/2] net: mana: force full-page RX buffers via ethtool private flag --- commit 2ea505589c71d255969461add82f06436f8f8e80
Author: Dipayaan Roy <[email protected]>
net: mana: force full-page RX buffers via ethtool private flag
This commit adds an ethtool private flag to force one RX buffer per page, bypassing the page_pool fragment path. This is intended to restore line-rate throughput on certain ARM64 platforms with 4K PAGE_SIZE.
Quoted 4 lines
drivers/net/ethernet/microsoft/mana/mana_ethtool.c +0
-0
[ ... ]
Quoted 1 line
drivers/net/ethernet/microsoft/mana/mana_ethtool.c +0
-0@@ -756,6 +775,78 @@ static int mana_get_link_ksettings(struct net_device *ndev,
[ ... ]
Quoted 2 lines
drivers/net/ethernet/microsoft/mana/mana_ethtool.c +2
-0+static int mana_set_priv_flags (struct net_device *ndev,u32 priv_flags) +{
[ ... ]
Quoted 1 line
drivers/net/ethernet/microsoft/mana/mana_ethtool.c +1
-0+if (changed &BIT (MANA_PRIV_FLAG_USE_FULL_PAGE_RXBUF )) {
[ ... ]
drivers/net/ethernet/microsoft/mana/mana_ethtool.c static int mana_get_link_ksettings(struct net_device *ndev, · line 824
Quoted 7 lines
drivers/net/ethernet/microsoft/mana/mana_ethtool.c +7
-0+ err =mana_pre_alloc_rxbufs (apc, ndev->mtu, apc->num_queues); +if (err) { +netdev_err (ndev, +"Insufficient memory for new allocations\n" ); + apc->priv_flags = old_priv_flags; + goto clear_flag; + }
[Severity: High]
This isn't a bug introduced by this patch, but while reviewing the callers of mana_pre_alloc_rxbufs(), does a failure during XDP setup leave a dangling pointer?
In drivers/net/ethernet/microsoft/mana/mana_bpf.c:mana_xdp_set(), apc->bpf_prog is updated before the allocation:
apc->bpf_prog = prog;
If the allocation fails, the function returns early without cleaning up:
err = mana_pre_alloc_rxbufs(apc, ndev->mtu, apc->num_queues);
if (err) {
NL_SET_ERR_MSG_MOD(extack,
"XDP: Insufficient memory ...");
return err;
}The core network stack handles the error by releasing its reference to the new BPF program, which may then be freed. Because the early return skips the err_dealloc_rxbuffs label, apc->bpf_prog is never reverted to old_prog. Could a subsequent interface flap execute mana_attach() and assign this freed BPF program to the hardware RX queues, causing a use-after-free?
Signature · 1 line
Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=2
Re: [PATCH net-next v13 2/2] net: mana: force full-page RX buffers via ethtool private flag
Quoted 55 lines · On Thu, Jul 30, 2026 at 06:34:37AM +0000, [email protected] wrote:
Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
Pre-existing issues:
- [High] Use-after-free of BPF program whenmana_pre_alloc_rxbufsfails during XDP setup ----- Patch [2]: [PATCH net-next v13 2/2] net: mana: force full-page RX buffers via ethtool private flag --- commit
2ea505589c71d255969461add82f06436f8f8e80
Author: Dipayaan Roy <[email protected]>net: mana: force full-page RX buffers via ethtool private flag
This commit adds an ethtool private flag to force one RX buffer per page, bypassing the
page_poolfragment path. This is intended to restore line-rate throughput on certain ARM64 platforms with 4KPAGE_SIZE.Quoted 4 lines
drivers/net/ethernet/microsoft/mana/mana_ethtool.c +0
-0[ ... ]
Quoted 1 line
drivers/net/ethernet/microsoft/mana/mana_ethtool.c +0
-0@@ -756,6 +775,78 @@ static int mana_get_link_ksettings(struct net_device *ndev,[ ... ]
Quoted 2 lines
drivers/net/ethernet/microsoft/mana/mana_ethtool.c +2
-0+static int mana_set_priv_flags (struct net_device *ndev,u32 priv_flags) +{[ ... ]
Quoted 1 line
drivers/net/ethernet/microsoft/mana/mana_ethtool.c +1
-0+if (changed &BIT (MANA_PRIV_FLAG_USE_FULL_PAGE_RXBUF )) {[ ... ]
drivers/net/ethernet/microsoft/mana/mana_ethtool.c static int mana_get_link_ksettings(struct net_device *ndev, · line 824
Quoted 7 lines
drivers/net/ethernet/microsoft/mana/mana_ethtool.c +7
-0+ err =mana_pre_alloc_rxbufs (apc, ndev->mtu, apc->num_queues); +if (err) { +netdev_err (ndev, +"Insufficient memory for new allocations\n" ); + apc->priv_flags = old_priv_flags; + goto clear_flag; + }[Severity: High]
This isn't a bug introduced by this patch, but while reviewing the callers ofmana_pre_alloc_rxbufs(), does a failure during XDP setup leave a dangling pointer?In drivers/net/ethernet/microsoft/mana/mana_bpf.c:mana_xdp_set(),
apc->bpf_progis updated before the allocation:apc->bpf_prog = prog;If the allocation fails, the function returns early without cleaning up:
err = mana_pre_alloc_rxbufs(apc, ndev->mtu, apc->num_queues); if (err) { NL_SET_ERR_MSG_MOD(extack, "XDP: Insufficient memory ..."); return err; }
Quoted 8 lines
The core network stack handles the error by releasing its reference to the new BPF program, which may then be freed. Because the early return skips the
err_dealloc_rxbuffslabel,apc->bpf_progis never reverted toold_prog. Could a subsequent interface flap executemana_attach()and assign this freed BPF program to the hardware RX queues, causing a use-after-free?Signature · 1 line
Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=2
As this Sashiko comment is for a pre-exisiting issue and not related to this patch, will send out a different patch for this.
Regards
Dipayaan Roy
This series was applied to netdev/net-next.git (main) by Jakub Kicinski <[email protected]>:
Hello:
This series was applied to netdev/net-next.git (main) by Jakub Kicinski <[email protected]>:
Quoted 8 lines · On Tue, 28 Jul 2026 23:21:27 -0700 you wrote:
On some ARM64 platforms with 4K
PAGE_SIZE, utilizingpage_poolfragments for allocation in the RX refill path (~2kB buffer per fragment) causes 15-20% throughput regression under high connection counts (>16 TCP streams at 180+ Gbps). Using full-page buffers on these platforms shows no regression and restores line-rate performance.[...]
Here is the summary with links:
- [net-next,v13,1/2] net: mana: refactor mana_get_strings() and mana_get_sset_count() to use switch
https://git.kernel.org/netdev/net-next/c/d52f80731055 - [net-next,v13,2/2] net: mana: force full-page RX buffers via ethtool private flag https://git.kernel.org/netdev/net-next/c/5b5cb75fb86a
You are awesome, thank you!
Signature · 2 lines
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