[RFC PATCH v2 4/9] igb: Add VF post-load fixups for live migration

["Cédric Le Goater" <clg@redhat.com>]

After restoring per-VF register state, propagate the VF's PVT shadow
values back into the PF's aggregate EIMS/EIAC/EIAM registers and
re-apply the VTIVAR interrupt vector routing to the shared IVAR0.

AI-used-for: analysis, code (prototype)
Signed-off-by: Cédric Le Goater <clg@redhat.com>
---
 hw/net/igb_core.h      |  3 ++
 hw/net/igb_core.c      | 66 ++++++++++++++++++++++++++++++++++++++++++
 hw/net/igb_migration.c |  7 +++++
 3 files changed, 76 insertions(+)

diff --git a/hw/net/igb_core.h b/hw/net/igb_core.h
index 60724e2824ab..22e10e4e6d0b 100644
--- a/hw/net/igb_core.h
+++ b/hw/net/igb_core.h
@@ -145,4 +145,7 @@ igb_start_recv(IGBCore *core);
 
 IGBCore *igb_pf_get_core(void *pf);
 
+void igb_core_vf_propagate_irqs(IGBCore *core, uint16_t vfn);
+void igb_core_vf_propagate_ivar(IGBCore *core, uint16_t vfn);
+
 #endif
diff --git a/hw/net/igb_core.c b/hw/net/igb_core.c
index 2a4883907353..01745fe756d0 100644
--- a/hw/net/igb_core.c
+++ b/hw/net/igb_core.c
@@ -4552,3 +4552,69 @@ igb_core_post_load(IGBCore *core)
 
     return 0;
 }
+
+/*
+ * Propagate VF interrupt state to PF aggregates after loading VF
+ * registers. The load path writes directly to mac[] bypassing the
+ * register handlers that OR VF bits into EIMS/EIAC/EIAM. Also clear
+ * stale VF bits in EICR that may have been set by packets arriving
+ * between PF vmstate restore and VF state load.
+ */
+void igb_core_vf_propagate_irqs(IGBCore *core, uint16_t vfn)
+{
+    uint32_t shift = 22 - vfn * IGBVF_MSIX_VEC_NUM;
+    uint32_t vf_mask = 0x7 << shift;
+    uint32_t pvt_idx;
+
+    core->mac[EIMS] &= ~vf_mask;
+    pvt_idx = PVTEIMS0 + vfn * 0x40;
+    core->mac[EIMS] |= (core->mac[pvt_idx] & 0x7) << shift;
+
+    core->mac[EIAC] &= ~vf_mask;
+    pvt_idx = PVTEIAC0 + vfn * 0x40;
+    core->mac[EIAC] |= (core->mac[pvt_idx] & 0x7) << shift;
+
+    core->mac[EIAM] &= ~vf_mask;
+    pvt_idx = PVTEIAM0 + vfn * 0x40;
+    core->mac[EIAM] |= (core->mac[pvt_idx] & 0x7) << shift;
+
+    core->mac[EICR] &= ~vf_mask;
+}
+
+/*
+ * Re-apply VTIVAR -> IVAR0 interrupt routing. The L1 PF driver
+ * may have overwritten the shared IVAR0 entries with its own
+ * queue routing after L0 vmstate restore.
+ */
+void igb_core_vf_propagate_ivar(IGBCore *core, uint16_t vfn)
+{
+    uint32_t vtivar = core->mac[VTIVAR + vfn];
+    int n;
+    uint8_t ent;
+    uint32_t mask;
+
+    n = igb_ivar_entry_rx(vfn);
+    mask = 0xffU << (8 * (n % 4));
+    if (vtivar & E1000_IVAR_VALID) {
+        ent = E1000_IVAR_VALID |
+              (24 - vfn * IGBVF_MSIX_VEC_NUM - (2 - (vtivar & 0x7)));
+        core->mac[IVAR0 + n / 4] =
+            (core->mac[IVAR0 + n / 4] & ~mask) |
+            ((uint32_t)ent << (8 * (n % 4)));
+    } else {
+        core->mac[IVAR0 + n / 4] &= ~mask;
+    }
+
+    n = igb_ivar_entry_tx(vfn);
+    mask = 0xffU << (8 * (n % 4));
+    ent = vtivar >> 8;
+    if (ent & E1000_IVAR_VALID) {
+        ent = E1000_IVAR_VALID |
+              (24 - vfn * IGBVF_MSIX_VEC_NUM - (2 - (ent & 0x7)));
+        core->mac[IVAR0 + n / 4] =
+            (core->mac[IVAR0 + n / 4] & ~mask) |
+            ((uint32_t)ent << (8 * (n % 4)));
+    } else {
+        core->mac[IVAR0 + n / 4] &= ~mask;
+    }
+}
diff --git a/hw/net/igb_migration.c b/hw/net/igb_migration.c
index c34035974620..af7257ccc4fd 100644
--- a/hw/net/igb_migration.c
+++ b/hw/net/igb_migration.c
@@ -384,12 +384,19 @@ static int igb_core_vf_load_state(IgbVfState *s, const void *buf, size_t size)
 static int igbvf_mig_load(IgbVfState *s, const void *buf, size_t size)
 {
     int ret;
+    IGBCore *core = igbvf_get_core(s);
 
     ret = igb_core_vf_load_state(s, buf, size);
     if (ret < 0) {
         return ret;
     }
 
+    /*
+     * Post-load: sync VF interrupt and routing state to PF aggregates
+     */
+    igb_core_vf_propagate_irqs(core, s->vfn);
+    igb_core_vf_propagate_ivar(core, s->vfn);
+
     return 0;
 }
 
-- 
2.55.0