Re: [PATCH v4 3/7] igb: Implement TRL register write and configuration

[Akihiko Odaki]

On 2026/06/16 7:18, Josh Hilke wrote:
Implement write handlers for TLDQSEL and TRLRC registers to allow the
guest to configure Transmit Rate Limiting. Translate the register Rate
Factor into a physical target rate (bytes/sec) per queue.  Disable TRL
and clear timers when the link status changes or when TRL is disabled by
the guest.
Signed-off-by: Josh Hilke <jrhi...@google.com>
---
  hw/net/igb_core.c | 57 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-
  1 file changed, 56 insertions(+), 1 deletion(-)

diff --git a/hw/net/igb_core.c b/hw/net/igb_core.c
index c94e8d3..dea8136 100644
--- a/hw/net/igb_core.c
+++ b/hw/net/igb_core.c
@@ -2137,11 +2137,27 @@ igb_set_phy_ctrl(IGBCore *core, uint16_t val)
      }
  }
  
+static void igb_trl_disable_queue(IGBCore *core, int qidx)
+{
+    core->trl[qidx].trlrc = 0;
+
+    timer_del(core->trl[qidx].timer);
+}
+
+static void igb_trl_disable(IGBCore *core)
+{
+    for (int i = 0; i < IGB_NUM_QUEUES; i++) {
+        igb_trl_disable_queue(core, i);
+    }
+}
+
  void igb_core_set_link_status(IGBCore *core)
  {
      NetClientState *nc = qemu_get_queue(core->owner_nic);
      uint32_t old_status = core->mac[STATUS];
  
+    igb_trl_disable(core);
+
      trace_e1000e_link_status_changed(nc->link_down ? false : true);
  
      if (nc->link_down) {
@@ -2624,6 +2640,42 @@ static void igb_set_vtivar(IGBCore *core, int index, 
uint32_t val)
       */
  }
  
+static uint32_t igb_get_trlrc(IGBCore *core, int index)
+{
+    int qidx = core->mac[TRLDQSEL];
+
+    return core->trl[qidx].trlrc;
+}
+
+static void igb_set_trldqsel(IGBCore *core, int index, uint32_t val)
+{
+    core->mac[index] = val & 0xF;
+}
+
+static void igb_set_trlrc(IGBCore *core, int index, uint32_t val)
+{
+    uint64_t rf_scaled;
+    int qidx;
+
+    qidx = core->mac[TRLDQSEL];
+    core->trl[qidx].trlrc = val;
+
+    if (!igb_trl_enabled(val)) {
+        goto disable;
+    }
+
+    rf_scaled = igb_trl_get_scaled_rate_factor(val);
+
+    /* Zero is not a valid rate factor, treat as disabled */
+    if (rf_scaled == 0) {
+        goto disable;
+    }
+    return;
+
+disable:
+    igb_trl_disable_queue(core, qidx);

This behavior of overwriting TRLRC and dropping the pending work is not 
specified in the datasheet and extraneous.

Regards,
Akihiko Odaki

+}
+
  static inline void
  igb_autoneg_timer(void *opaque)
  {
@@ -3679,6 +3731,7 @@ static const readops igb_macreg_readops[] = {
      [RQDPC15] = igb_mac_read_clr4,
      [VTIVAR ... VTIVAR + 7] = igb_mac_readreg,
      [VTIVAR_MISC ... VTIVAR_MISC + 7] = igb_mac_readreg,
+    [TRLRC] = igb_get_trlrc,
  };
  enum { IGB_NREADOPS = ARRAY_SIZE(igb_macreg_readops) };
  
@@ -4127,7 +4180,9 @@ static const writeops igb_macreg_writeops[] = {
      [PVTEICR6] = igb_set_vteicr,
      [PVTEICR7] = igb_set_vteicr,
      [VTIVAR ... VTIVAR + 7] = igb_set_vtivar,
-    [VTIVAR_MISC ... VTIVAR_MISC + 7] = igb_mac_writereg
+    [VTIVAR_MISC ... VTIVAR_MISC + 7] = igb_mac_writereg,
+    [TRLDQSEL] = igb_set_trldqsel,
+    [TRLRC]    = igb_set_trlrc
  };
  enum { IGB_NWRITEOPS = ARRAY_SIZE(igb_macreg_writeops) };