Re: [PATCH V1] vfio: fix sub-page bar after cpr

["Cédric Le Goater" <clg@redhat.com>]

On 7/14/25 21:21, Steve Sistare wrote:
> Regions for sub-page BARs are normally mapped here, in response to the
> guest writing to PCI config space:
> 
>    vfio_pci_write_config()
>      pci_default_write_config()
>        pci_update_mappings()
>          memory_region_add_subregion()
>      vfio_sub_page_bar_update_mapping()
>        ... vfio_dma_map()
> 
> However, after CPR, the guest does not reconfigure the device and the
> code path above is not taken.  To fix, in vfio_cpr_pci_post_load, call
> vfio_sub_page_bar_update_mapping for each sub-page BAR with a valid
> address.
> 
> Fixes: 7e9f21411302 ("vfio/container: restore DMA vaddr")
> 
> Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
> ---
>   hw/vfio/pci.h |  1 +
>   hw/vfio/cpr.c |  2 ++
>   hw/vfio/pci.c | 14 ++++++++++++++
>   3 files changed, 17 insertions(+)
> 
> diff --git a/hw/vfio/pci.h b/hw/vfio/pci.h
> index 495fae7..cb1310d 100644
> --- a/hw/vfio/pci.h
> +++ b/hw/vfio/pci.h
> @@ -228,6 +228,7 @@ void vfio_pci_write_config(PCIDevice *pdev,
>   uint64_t vfio_vga_read(void *opaque, hwaddr addr, unsigned size);
>   void vfio_vga_write(void *opaque, hwaddr addr, uint64_t data, unsigned size);
>   
> +void vfio_sub_page_bar_update_mappings(VFIOPCIDevice *vdev);
>   bool vfio_opt_rom_in_denylist(VFIOPCIDevice *vdev);
>   bool vfio_config_quirk_setup(VFIOPCIDevice *vdev, Error **errp);
>   void vfio_vga_quirk_setup(VFIOPCIDevice *vdev);

We should rename all this routines.  For later.

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

Thanks,

C.


> diff --git a/hw/vfio/cpr.c b/hw/vfio/cpr.c
> index af0f12a..384b56c 100644
> --- a/hw/vfio/cpr.c
> +++ b/hw/vfio/cpr.c
> @@ -116,6 +116,8 @@ static int vfio_cpr_pci_post_load(void *opaque, int version_id)
>       PCIDevice *pdev = &vdev->pdev;
>       int nr_vectors;
>   
> +    vfio_sub_page_bar_update_mappings(vdev);
> +
>       if (msix_enabled(pdev)) {
>           vfio_pci_msix_set_notifiers(vdev);
>           nr_vectors = vdev->msix->entries;
> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
> index 1093b28..9c616bd 100644
> --- a/hw/vfio/pci.c
> +++ b/hw/vfio/pci.c
> @@ -2826,6 +2826,20 @@ static int vfio_pci_load_config(VFIODevice *vbasedev, QEMUFile *f)
>       return ret;
>   }
>   
> +void vfio_sub_page_bar_update_mappings(VFIOPCIDevice *vdev)
> +{
> +    PCIDevice *pdev = &vdev->pdev;
> +    int page_size = qemu_real_host_page_size();
> +    int bar;
> +
> +    for (bar = 0; bar < PCI_ROM_SLOT; bar++) {
> +        PCIIORegion *r = &pdev->io_regions[bar];
> +        if (r->addr != PCI_BAR_UNMAPPED && r->size > 0 && r->size < page_size) {
> +            vfio_sub_page_bar_update_mapping(pdev, bar);
> +        }
> +    }
> +}
> +
>   static VFIODeviceOps vfio_pci_ops = {
>       .vfio_compute_needs_reset = vfio_pci_compute_needs_reset,
>       .vfio_hot_reset_multi = vfio_pci_hot_reset_multi,