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

["Cédric Le Goater" <clg@redhat.com>]

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.duan@intel.com>


Reviewed-by: Cédric Le Goater <clg@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;
>       }
>