From 5e4f5ad8563b793b79a48e0eb52ee31beb585fff Mon Sep 17 00:00:00 2001
From: xiaotianxt <me@xiaotian.dev>
Date: Tue, 11 Aug 2026 19:07:13 -0400
Subject: [PATCH] Fix DMA page lookup for IOMMU allocations

---
 modules/exanic/exanic-dev.c  | 4 ++--
 modules/exanic/exanic-main.c | 9 ++++++---
 modules/exanic/exanic.h      | 8 ++++++++
 3 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/modules/exanic/exanic-dev.c b/modules/exanic/exanic-dev.c
index 8bf985f..edbaf40 100644
--- a/modules/exanic/exanic-dev.c
+++ b/modules/exanic/exanic-dev.c
@@ -350,7 +350,7 @@ static int exanic_map_tx_feedback(struct exanic *exanic,
     for (off = 0; off < map_size; off += PAGE_SIZE)
     {
         err = vm_insert_page(vma, vma->vm_start + off,
-                virt_to_page(exanic->tx_feedback_virt + off));
+                exanic_virt_to_page(exanic->tx_feedback_virt + off));
         if (err)
         {
             phys_addr = virt_to_phys(exanic->tx_feedback_virt + off);
@@ -488,7 +488,7 @@ static int exanic_map_rx_region(struct exanic *exanic, struct vm_area_struct *vm
     for (off = 0; off < map_size; off += PAGE_SIZE)
     {
         err = vm_insert_page(vma, vma->vm_start + off,
-                virt_to_page(rx_region_virt + off));
+                exanic_virt_to_page(rx_region_virt + off));
         if (err)
         {
             phys_addr = virt_to_phys(rx_region_virt + off);
diff --git a/modules/exanic/exanic-main.c b/modules/exanic/exanic-main.c
index 14b7d55..eecfc17 100644
--- a/modules/exanic/exanic-main.c
+++ b/modules/exanic/exanic-main.c
@@ -132,7 +132,8 @@ bool exanic_rx_in_use(struct exanic *exanic, unsigned port_num)
     if (exanic->port[port_num].rx_region_virt)
     {
         /* Check if the region is mapped */
-        if (page_count(virt_to_page(exanic->port[port_num].rx_region_virt)) > 1)
+        if (page_count(exanic_virt_to_page(
+                exanic->port[port_num].rx_region_virt)) > 1)
             return true;
     }
 
@@ -158,7 +159,8 @@ int exanic_count_tx_feedback_users(struct exanic *exanic)
     {
         for (i = 0; i < EXANIC_TX_FEEDBACK_NUM_PAGES; i++)
             /* subtract 1 since we have a mapping */
-            count += page_count(virt_to_page(exanic->tx_feedback_virt + i * PAGE_SIZE)) - 1;
+            count += page_count(exanic_virt_to_page(
+                    exanic->tx_feedback_virt + i * PAGE_SIZE)) - 1;
 
         return count;
     }
@@ -178,7 +180,8 @@ int exanic_count_rx_users(struct exanic *exanic)
     {
         if (exanic->port[i].rx_region_virt)
             /* subtract 1 since we have a mapping */
-            count += page_count(virt_to_page(exanic->port[i].rx_region_virt)) - 1;
+            count += page_count(exanic_virt_to_page(
+                    exanic->port[i].rx_region_virt)) - 1;
 
         for (buf = 0; buf < exanic->max_filter_buffers; buf++)
             count += exanic->port[i].filter_buffers[buf].refcount;
diff --git a/modules/exanic/exanic.h b/modules/exanic/exanic.h
index 457a770..3c0c13a 100644
--- a/modules/exanic/exanic.h
+++ b/modules/exanic/exanic.h
@@ -6,6 +6,8 @@
 #ifndef _EXANIC_H_
 #define _EXANIC_H_
 
+#include <linux/mm.h>
+
 #include "../../include/exanic_version.h"
 
 #define DRV_VERSION EXANIC_VERSION_TEXT
@@ -69,6 +71,12 @@ struct exanic_ate_regdump
 /* exanic.c */
 struct exanic;
 
+/* dma_alloc_coherent() may return an address in vmalloc space. */
+static inline struct page *exanic_virt_to_page(const void *addr)
+{
+    return is_vmalloc_addr(addr) ? vmalloc_to_page(addr) : virt_to_page(addr);
+}
+
 struct exanic *exanic_find_by_minor(unsigned minor);
 
 void exanic_netdev_get_id_and_port(struct net_device *ndev,