FAILED: patch "[PATCH] i40e: Enforce software interrupt during busy-poll exit" failed to apply to 6.1-stable tree

The patch below does not apply to the 6.1-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y
git checkout FETCH_HEAD
git cherry-pick -x ea558de7238bb12c3435c47f0631e9d17bf4a09f
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2024040500-scalping-relatable-1383@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From ea558de7238bb12c3435c47f0631e9d17bf4a09f Mon Sep 17 00:00:00 2001
From: Ivan Vecera <[email protected]>
Date: Sat, 16 Mar 2024 12:38:29 +0100
Subject: [PATCH] i40e: Enforce software interrupt during busy-poll exit

As for ice bug fixed by commit b7306b42beaf ("ice: manage interrupts during poll exit") followed by commit 23be7075b318 ("ice: fix software generating extra interrupts") I'm seeing the similar issue also with i40e driver.

In certain situation when busy-loop is enabled together with adaptive coalescing, the driver occasionally misses that there are outstanding descriptors to clean when exiting busy poll.

Try to catch the remaining work by triggering a software interrupt when exiting busy poll. No extra interrupts will be generated when busy polling is not used.

The issue was found when running sockperf ping-pong tcp test with adaptive coalescing and busy poll enabled (50 as value busy_pool and busy_read sysctl knobs) and results in huge latency spikes with more than 100000us.

The fix is inspired from the ice driver and do the following:
1) During napi poll exit in case of busy-poll (napo_complete_done() returns false) this is recorded to q_vector that we were in busy loop.
2) Extends i40e_buildreg_itr() to be able to add an enforced software interrupt into built value
2) In i40e_update_enable_itr() enforces a software interrupt trigger if we are exiting busy poll to catch any pending clean-ups
3) Reuses unused 3rd ITR (interrupt throttle) index and set it to 20K interrupts per second to limit the number of these sw interrupts.

Test results
============
Prior:
[root@dell-per640-07 net]# sockperf ping-pong -i 10.9.9.1 --tcp -m 1000 --mps=max -t 120
sockperf: == version #3.10-no.git ==
sockperf[CLIENT] send on:sockperf: using recvfrom() to block on socket(s)

[ 0] IP = 10.9.9.1 PORT = 11111 # TCP
sockperf: Warmup stage (sending a few dummy messages)...
sockperf: Starting test...
sockperf: Test end (interrupted by timer)
sockperf: Test ended
sockperf: [Total Run] RunTime=119.999 sec; Warm up time=400 msec; SentMessages=2438563; ReceivedMessages=2438562
sockperf: ========= Printing statistics for Server No: 0
sockperf: [Valid Duration] RunTime=119.549 sec; SentMessages=2429473; ReceivedMessages=2429473
sockperf: ====> avg-latency=24.571 (std-dev=93.297, mean-ad=4.904, median-ad=1.510, siqr=1.063, cv=3.797, std-error=0.060, 99.0% ci=[24.417, 24.725])
sockperf: # dropped messages = 0; # duplicated messages = 0; # out-of-order messages = 0
sockperf: Summary: Latency is 24.571 usec
sockperf: Total 2429473 observations; each percentile contains 24294.73 observations
sockperf: ---> <MAX> observation = 103294.331
sockperf: ---> percentile 99.999 = 45.633
sockperf: ---> percentile 99.990 = 37.013
sockperf: ---> percentile 99.900 = 35.910
sockperf: ---> percentile 99.000 = 33.390
sockperf: ---> percentile 90.000 = 28.626
sockperf: ---> percentile 75.000 = 27.741
sockperf: ---> percentile 50.000 = 26.743
sockperf: ---> percentile 25.000 = 25.614
sockperf: ---> <MIN> observation = 12.220

After:
[root@dell-per640-07 net]# sockperf ping-pong -i 10.9.9.1 --tcp -m 1000 --mps=max -t 120
sockperf: == version #3.10-no.git ==
sockperf[CLIENT] send on:sockperf: using recvfrom() to block on socket(s)

[ 0] IP = 10.9.9.1 PORT = 11111 # TCP
sockperf: Warmup stage (sending a few dummy messages)...
sockperf: Starting test...
sockperf: Test end (interrupted by timer)
sockperf: Test ended
sockperf: [Total Run] RunTime=119.999 sec; Warm up time=400 msec; SentMessages=2400055; ReceivedMessages=2400054
sockperf: ========= Printing statistics for Server No: 0
sockperf: [Valid Duration] RunTime=119.549 sec; SentMessages=2391186; ReceivedMessages=2391186
sockperf: ====> avg-latency=24.965 (std-dev=5.934, mean-ad=4.642, median-ad=1.485, siqr=1.067, cv=0.238, std-error=0.004, 99.0% ci=[24.955, 24.975])
sockperf: # dropped messages = 0; # duplicated messages = 0; # out-of-order messages = 0
sockperf: Summary: Latency is 24.965 usec
sockperf: Total 2391186 observations; each percentile contains 23911.86 observations
sockperf: ---> <MAX> observation = 195.841
sockperf: ---> percentile 99.999 = 45.026
sockperf: ---> percentile 99.990 = 39.009
sockperf: ---> percentile 99.900 = 35.922
sockperf: ---> percentile 99.000 = 33.482
sockperf: ---> percentile 90.000 = 28.902
sockperf: ---> percentile 75.000 = 27.821
sockperf: ---> percentile 50.000 = 26.860
sockperf: ---> percentile 25.000 = 25.685
sockperf: ---> <MIN> observation = 12.277

index ba24f3fa92c3..2fbabcdb5bb5 100644
@@ -955,6 +955,7 @@ struct i40e_q_vector {
 	struct rcu_head rcu;	/* to avoid race with update stats on free */
 	char name[I40E_INT_NAME_STR_LEN];
 	bool arm_wb_state;
+	bool in_busy_poll;
 	int irq_num;		/* IRQ assigned to this q_vector */
 } ____cacheline_internodealigned_in_smp;
 

index f86578857e8a..6576a0081093 100644
@@ -3911,6 +3911,12 @@ static void i40e_vsi_configure_msix(struct i40e_vsi *vsi)
 		     q_vector->tx.target_itr >> 1);
 		q_vector->tx.current_itr = q_vector->tx.target_itr;
 
+		/* Set ITR for software interrupts triggered after exiting
+		 * busy-loop polling.
+		 */
+		wr32(hw, I40E_PFINT_ITRN(I40E_SW_ITR, vector - 1),
+		     I40E_ITR_20K);
+
 		wr32(hw, I40E_PFINT_RATEN(vector - 1),
 		     i40e_intrl_usec_to_reg(vsi->int_rate_limit));
 

index 14ab642cafdb..432afbb64201 100644
@@ -333,8 +333,11 @@
 #define I40E_PFINT_DYN_CTLN_ITR_INDX_SHIFT 3
 #define I40E_PFINT_DYN_CTLN_ITR_INDX_MASK I40E_MASK(0x3, I40E_PFINT_DYN_CTLN_ITR_INDX_SHIFT)
 #define I40E_PFINT_DYN_CTLN_INTERVAL_SHIFT 5
+#define I40E_PFINT_DYN_CTLN_INTERVAL_MASK I40E_MASK(0xFFF, I40E_PFINT_DYN_CTLN_INTERVAL_SHIFT)
 #define I40E_PFINT_DYN_CTLN_SW_ITR_INDX_ENA_SHIFT 24
 #define I40E_PFINT_DYN_CTLN_SW_ITR_INDX_ENA_MASK I40E_MASK(0x1, I40E_PFINT_DYN_CTLN_SW_ITR_INDX_ENA_SHIFT)
+#define I40E_PFINT_DYN_CTLN_SW_ITR_INDX_SHIFT 25
+#define I40E_PFINT_DYN_CTLN_SW_ITR_INDX_MASK I40E_MASK(0x3, I40E_PFINT_DYN_CTLN_SW_ITR_INDX_SHIFT)
 #define I40E_PFINT_ICR0 0x00038780 /* Reset: CORER */
 #define I40E_PFINT_ICR0_INTEVENT_SHIFT 0
 #define I40E_PFINT_ICR0_INTEVENT_MASK I40E_MASK(0x1, I40E_PFINT_ICR0_INTEVENT_SHIFT)

index abf15067eb5d..2cdc7de6301c 100644
@@ -68,6 +68,7 @@ enum i40e_dyn_idx {
 /* these are indexes into ITRN registers */
 #define I40E_RX_ITR    I40E_IDX_ITR0
 #define I40E_TX_ITR    I40E_IDX_ITR1
+#define I40E_SW_ITR    I40E_IDX_ITR2
 
 /* Supported RSS offloads */
 #define I40E_DEFAULT_RSS_HENA ( \