diff options
Diffstat (limited to 'package/kernel/mac80211/patches/subsys/330-mac80211-fix-overflow-issues-in-airtime-fairness-cod.patch')
| -rw-r--r-- | package/kernel/mac80211/patches/subsys/330-mac80211-fix-overflow-issues-in-airtime-fairness-cod.patch | 132 |
1 files changed, 132 insertions, 0 deletions
diff --git a/package/kernel/mac80211/patches/subsys/330-mac80211-fix-overflow-issues-in-airtime-fairness-cod.patch b/package/kernel/mac80211/patches/subsys/330-mac80211-fix-overflow-issues-in-airtime-fairness-cod.patch new file mode 100644 index 0000000000..037ab8e180 --- /dev/null +++ b/package/kernel/mac80211/patches/subsys/330-mac80211-fix-overflow-issues-in-airtime-fairness-cod.patch @@ -0,0 +1,132 @@ +From: Felix Fietkau <nbd@nbd.name> +Date: Sat, 28 May 2022 16:44:53 +0200 +Subject: [PATCH] mac80211: fix overflow issues in airtime fairness code + +The airtime weight calculation overflows with a default weight value of 256 +whenever more than 8ms worth of airtime is reported. +Bigger weight values impose even smaller limits on maximum airtime values. +This can mess up airtime based calculations for drivers that don't report +per-PPDU airtime values, but batch up values instead. + +Fix this by reordering multiplications/shifts and by reducing unnecessary +intermediate precision (which was lost in a later stage anyway). + +The new shift value limits the maximum weight to 4096, which should be more +than enough. Any values bigger than that will be clamped to the upper limit. + +Signed-off-by: Felix Fietkau <nbd@nbd.name> +--- + +--- a/net/mac80211/ieee80211_i.h ++++ b/net/mac80211/ieee80211_i.h +@@ -1666,50 +1666,34 @@ static inline struct airtime_info *to_ai + /* To avoid divisions in the fast path, we keep pre-computed reciprocals for + * airtime weight calculations. There are two different weights to keep track + * of: The per-station weight and the sum of weights per phy. +- * +- * For the per-station weights (kept in airtime_info below), we use 32-bit +- * reciprocals with a devisor of 2^19. This lets us keep the multiplications and +- * divisions for the station weights as 32-bit operations at the cost of a bit +- * of rounding error for high weights; but the choice of divisor keeps rounding +- * errors <10% for weights <2^15, assuming no more than 8ms of airtime is +- * reported at a time. +- * +- * For the per-phy sum of weights the values can get higher, so we use 64-bit +- * operations for those with a 32-bit divisor, which should avoid any +- * significant rounding errors. ++ * The per-sta shift value supports weight values of 1-4096 + */ +-#define IEEE80211_RECIPROCAL_DIVISOR_64 0x100000000ULL +-#define IEEE80211_RECIPROCAL_SHIFT_64 32 +-#define IEEE80211_RECIPROCAL_DIVISOR_32 0x80000U +-#define IEEE80211_RECIPROCAL_SHIFT_32 19 ++#define IEEE80211_RECIPROCAL_SHIFT_SUM 24 ++#define IEEE80211_RECIPROCAL_SHIFT_STA 12 ++#define IEEE80211_WEIGHT_SHIFT 8 + +-static inline void airtime_weight_set(struct airtime_info *air_info, u16 weight) ++static inline void airtime_weight_set(struct airtime_info *air_info, u32 weight) + { ++ weight = min_t(u32, weight, BIT(IEEE80211_RECIPROCAL_SHIFT_STA)); + if (air_info->weight == weight) + return; + + air_info->weight = weight; +- if (weight) { +- air_info->weight_reciprocal = +- IEEE80211_RECIPROCAL_DIVISOR_32 / weight; +- } else { +- air_info->weight_reciprocal = 0; +- } ++ if (weight) ++ weight = BIT(IEEE80211_RECIPROCAL_SHIFT_STA) / weight; ++ air_info->weight_reciprocal = weight; + } + + static inline void airtime_weight_sum_set(struct airtime_sched_info *air_sched, +- int weight_sum) ++ u32 weight_sum) + { + if (air_sched->weight_sum == weight_sum) + return; + + air_sched->weight_sum = weight_sum; +- if (air_sched->weight_sum) { +- air_sched->weight_sum_reciprocal = IEEE80211_RECIPROCAL_DIVISOR_64; +- do_div(air_sched->weight_sum_reciprocal, air_sched->weight_sum); +- } else { +- air_sched->weight_sum_reciprocal = 0; +- } ++ if (weight_sum) ++ weight_sum = BIT(IEEE80211_RECIPROCAL_SHIFT_SUM) / weight_sum; ++ air_sched->weight_sum_reciprocal = weight_sum; + } + + /* A problem when trying to enforce airtime fairness is that we want to divide +--- a/net/mac80211/sta_info.c ++++ b/net/mac80211/sta_info.c +@@ -1894,9 +1894,9 @@ void ieee80211_register_airtime(struct i + { + struct ieee80211_sub_if_data *sdata = vif_to_sdata(txq->vif); + struct ieee80211_local *local = sdata->local; +- u64 weight_sum, weight_sum_reciprocal; + struct airtime_sched_info *air_sched; + struct airtime_info *air_info; ++ u64 weight_sum_reciprocal; + u32 airtime = 0; + + air_sched = &local->airtime[txq->ac]; +@@ -1907,27 +1907,21 @@ void ieee80211_register_airtime(struct i + if (local->airtime_flags & AIRTIME_USE_RX) + airtime += rx_airtime; + +- /* Weights scale so the unit weight is 256 */ +- airtime <<= 8; +- + spin_lock_bh(&air_sched->lock); + + air_info->tx_airtime += tx_airtime; + air_info->rx_airtime += rx_airtime; + +- if (air_sched->weight_sum) { +- weight_sum = air_sched->weight_sum; ++ if (air_sched->weight_sum) + weight_sum_reciprocal = air_sched->weight_sum_reciprocal; +- } else { +- weight_sum = air_info->weight; ++ else + weight_sum_reciprocal = air_info->weight_reciprocal; +- } + + /* Round the calculation of global vt */ +- air_sched->v_t += (u64)((airtime + (weight_sum >> 1)) * +- weight_sum_reciprocal) >> IEEE80211_RECIPROCAL_SHIFT_64; +- air_info->v_t += (u32)((airtime + (air_info->weight >> 1)) * +- air_info->weight_reciprocal) >> IEEE80211_RECIPROCAL_SHIFT_32; ++ air_sched->v_t += ((u64)airtime * weight_sum_reciprocal) >> ++ (IEEE80211_RECIPROCAL_SHIFT_SUM - IEEE80211_WEIGHT_SHIFT); ++ air_info->v_t += (airtime * air_info->weight_reciprocal) >> ++ (IEEE80211_RECIPROCAL_SHIFT_STA - IEEE80211_WEIGHT_SHIFT); + ieee80211_resort_txq(&local->hw, txq); + + spin_unlock_bh(&air_sched->lock); |