Re: [PATCH v6 19/22] vfio: Add a new element bypass_ro in VFIOContainerBase

[Cédric Le Goater]

On 9/18/25 10:57, Zhenzhong Duan wrote:

When bypass_ro is true, readonly memory section is bypassed from mapping
in the container.

This is a preparing patch to workaround Intel ERRATA_772415, see changelog
in next patch for details about the errata.

Signed-off-by: Zhenzhong Duan <zhenzhong.d...@intel.com>

Reviewed-by: Cédric Le Goater <c...@redhat.com>

Thanks,

C.

---
  include/hw/vfio/vfio-container-base.h |  1 +
  hw/vfio/listener.c                    | 21 ++++++++++++++-------
  2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/include/hw/vfio/vfio-container-base.h 
b/include/hw/vfio/vfio-container-base.h
index acbd48a18a..2b9fec217a 100644
--- a/include/hw/vfio/vfio-container-base.h
+++ b/include/hw/vfio/vfio-container-base.h
@@ -52,6 +52,7 @@ struct VFIOContainerBase {
      QLIST_HEAD(, VFIODevice) device_list;
      GList *iova_ranges;
      NotifierWithReturn cpr_reboot_notifier;
+    bool bypass_ro;
  };

#define TYPE_VFIO_IOMMU "vfio-iommu"

diff --git a/hw/vfio/listener.c b/hw/vfio/listener.c
index e093833165..581ebfda36 100644
--- a/hw/vfio/listener.c
+++ b/hw/vfio/listener.c
@@ -76,8 +76,13 @@ static bool vfio_log_sync_needed(const VFIOContainerBase 
*bcontainer)
      return true;
  }

-static bool vfio_listener_skipped_section(MemoryRegionSection *section)

+static bool vfio_listener_skipped_section(MemoryRegionSection *section,
+                                          bool bypass_ro)
  {
+    if (bypass_ro && section->readonly) {
+        return true;
+    }
+
      return (!memory_region_is_ram(section->mr) &&
              !memory_region_is_iommu(section->mr)) ||
             memory_region_is_protected(section->mr) ||
@@ -368,9 +373,9 @@ static bool 
vfio_known_safe_misalignment(MemoryRegionSection *section)
  }

static bool vfio_listener_valid_section(MemoryRegionSection *section,

-                                        const char *name)
+                                        bool bypass_ro, const char *name)
  {
-    if (vfio_listener_skipped_section(section)) {
+    if (vfio_listener_skipped_section(section, bypass_ro)) {
          trace_vfio_listener_region_skip(name,
                  section->offset_within_address_space,
                  section->offset_within_address_space +
@@ -497,7 +502,8 @@ void vfio_container_region_add(VFIOContainerBase 
*bcontainer,
      int ret;
      Error *err = NULL;

- if (!vfio_listener_valid_section(section, "region_add")) {

+    if (!vfio_listener_valid_section(section, bcontainer->bypass_ro,
+                                     "region_add")) {
          return;
      }

@@ -663,7 +669,8 @@ static void vfio_listener_region_del(MemoryListener *listener,

      int ret;
      bool try_unmap = true;

- if (!vfio_listener_valid_section(section, "region_del")) {

+    if (!vfio_listener_valid_section(section, bcontainer->bypass_ro,
+                                     "region_del")) {
          return;
      }

@@ -820,7 +827,7 @@ static void vfio_dirty_tracking_update(MemoryListener *listener,

          container_of(listener, VFIODirtyRangesListener, listener);
      hwaddr iova, end;

- if (!vfio_listener_valid_section(section, "tracking_update") ||

+    if (!vfio_listener_valid_section(section, false, "tracking_update") ||
          !vfio_get_section_iova_range(dirty->bcontainer, section,
                                       &iova, &end, NULL)) {
          return;
@@ -1214,7 +1221,7 @@ static void vfio_listener_log_sync(MemoryListener 
*listener,
      int ret;
      Error *local_err = NULL;

- if (vfio_listener_skipped_section(section)) {

+    if (vfio_listener_skipped_section(section, false)) {
          return;
      }