Re: [PATCH v4 18/20] vfio: Add a new element bypass_ro in VFIOContainerBase

[Cédric Le Goater]

On 7/29/25 11:20, Zhenzhong Duan wrote:

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

This is a preparing patch to workaround Intel ERRATA_772415.

Signed-off-by: Zhenzhong Duan <zhenzhong.d...@intel.com>
---
  include/hw/vfio/vfio-container-base.h |  1 +
  hw/vfio/listener.c                    | 13 +++++++++----
  2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/include/hw/vfio/vfio-container-base.h 
b/include/hw/vfio/vfio-container-base.h
index bded6e993f..31fd784d76 100644
--- a/include/hw/vfio/vfio-container-base.h
+++ b/include/hw/vfio/vfio-container-base.h
@@ -51,6 +51,7 @@ typedef struct VFIOContainerBase {
      QLIST_HEAD(, VFIODevice) device_list;
      GList *iova_ranges;
      NotifierWithReturn cpr_reboot_notifier;
+    bool bypass_ro;
  } VFIOContainerBase;

typedef struct VFIOGuestIOMMU {

diff --git a/hw/vfio/listener.c b/hw/vfio/listener.c
index f498e23a93..c64aa4539e 100644
--- a/hw/vfio/listener.c
+++ b/hw/vfio/listener.c
@@ -364,7 +364,8 @@ static bool 
vfio_known_safe_misalignment(MemoryRegionSection *section)
      return true;
  }

-static bool vfio_listener_valid_section(MemoryRegionSection *section,

+static bool vfio_listener_valid_section(VFIOContainerBase *bcontainer,
+                                        MemoryRegionSection *section,
                                          const char *name)

Instead of adding a 'VFIOContainerBase *' argument, I would add an
extra 'bool bypass_ro' argument.

Thanks,

C.

  {
      if (vfio_listener_skipped_section(section)) {
@@ -375,6 +376,10 @@ static bool 
vfio_listener_valid_section(MemoryRegionSection *section,
          return false;
      }

+ if (bcontainer && bcontainer->bypass_ro && section->readonly) {

+        return false;
+    }
+
      if (unlikely((section->offset_within_address_space &
                    ~qemu_real_host_page_mask()) !=
                   (section->offset_within_region & 
~qemu_real_host_page_mask()))) {
@@ -494,7 +499,7 @@ 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(bcontainer, section, "region_add")) {
          return;
      }

@@ -655,7 +660,7 @@ 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(bcontainer, section, "region_del")) {
          return;
      }

@@ -812,7 +817,7 @@ 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(NULL, section, "tracking_update") ||
          !vfio_get_section_iova_range(dirty->bcontainer, section,
                                       &iova, &end, NULL)) {
          return;