Re: [PATCH V3 31/42] vfio/iommufd: use IOMMU_IOAS_MAP_FILE

[Steven Sistare <steven.sistare@oracle.com>]

On 5/20/2025 8:27 AM, Cédric Le Goater wrote:
> On 5/12/25 17:32, Steve Sistare wrote:
>> Use IOMMU_IOAS_MAP_FILE when the mapped region is backed by a file.
>> Such a mapping can be preserved without modification during CPR,
>> because it depends on the file's address space, which does not change,
>> rather than on the process's address space, which does change.
>>
>> Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
>> ---
>>   hw/vfio/container-base.c              |  9 +++++++++
>>   hw/vfio/iommufd.c                     | 13 +++++++++++++
>>   include/hw/vfio/vfio-container-base.h |  3 +++
>>   3 files changed, 25 insertions(+)
>>
>> diff --git a/hw/vfio/container-base.c b/hw/vfio/container-base.c
>> index 8f43bc8..72a51a6 100644
>> --- a/hw/vfio/container-base.c
>> +++ b/hw/vfio/container-base.c
>> @@ -79,7 +79,16 @@ int vfio_container_dma_map(VFIOContainerBase *bcontainer,
>>                              RAMBlock *rb)
>>   {
>>       VFIOIOMMUClass *vioc = VFIO_IOMMU_GET_CLASS(bcontainer);
>> +    int mfd = rb ? qemu_ram_get_fd(rb) : -1;
>> +    if (mfd >= 0 && vioc->dma_map_file) {
>> +        unsigned long start = vaddr - qemu_ram_get_host_addr(rb);
>> +        unsigned long offset = qemu_ram_get_fd_offset(rb);
>> +
>> +        vioc->dma_map_file(bcontainer, iova, size, mfd, start + offset,
>> +                           readonly);
>> +        return 0;
>> +    }
>>       g_assert(vioc->dma_map);
>>       return vioc->dma_map(bcontainer, iova, size, vaddr, readonly);
>>   }
>> diff --git a/hw/vfio/iommufd.c b/hw/vfio/iommufd.c
>> index 167bda4..6eb417a 100644
>> --- a/hw/vfio/iommufd.c
>> +++ b/hw/vfio/iommufd.c
>> @@ -44,6 +44,18 @@ static int iommufd_cdev_map(const VFIOContainerBase *bcontainer, hwaddr iova,
>>                                      iova, size, vaddr, readonly);
>>   }
>> +static int iommufd_cdev_map_file(const VFIOContainerBase *bcontainer,
>> +                                 hwaddr iova, ram_addr_t size,
>> +                                 int fd, unsigned long start, bool readonly)
>> +{
>> +    const VFIOIOMMUFDContainer *container =
>> +        container_of(bcontainer, VFIOIOMMUFDContainer, bcontainer);
>> +
>> +    return iommufd_backend_map_file_dma(container->be,
>> +                                        container->ioas_id,
>> +                                        iova, size, fd, start, readonly);
>> +}
>> +
>>   static int iommufd_cdev_unmap(const VFIOContainerBase *bcontainer,
>>                                 hwaddr iova, ram_addr_t size,
>>                                 IOMMUTLBEntry *iotlb, bool unmap_all)
>> @@ -802,6 +814,7 @@ static void vfio_iommu_iommufd_class_init(ObjectClass *klass, const void *data)
>>       VFIOIOMMUClass *vioc = VFIO_IOMMU_CLASS(klass);
>>       vioc->dma_map = iommufd_cdev_map;
>> +    vioc->dma_map_file = iommufd_cdev_map_file;
>>       vioc->dma_unmap = iommufd_cdev_unmap;
>>       vioc->attach_device = iommufd_cdev_attach;
>>       vioc->detach_device = iommufd_cdev_detach;
>> diff --git a/include/hw/vfio/vfio-container-base.h b/include/hw/vfio/vfio-container-base.h
>> index 03b3f9c..f30f828 100644
>> --- a/include/hw/vfio/vfio-container-base.h
>> +++ b/include/hw/vfio/vfio-container-base.h
>> @@ -123,6 +123,9 @@ struct VFIOIOMMUClass {
>>       int (*dma_map)(const VFIOContainerBase *bcontainer,
>>                      hwaddr iova, ram_addr_t size,
>>                      void *vaddr, bool readonly);
>> +    int (*dma_map_file)(const VFIOContainerBase *bcontainer,
>> +                        hwaddr iova, ram_addr_t size,
>> +                        int fd, unsigned long start, bool readonly);
> 
> Please add documentation.

OK.  Using @dma_unmap as a template:

     /**
      * @dma_map_file
      *
      * Map a file range for the container.
      *
      * @bcontainer: #VFIOContainerBase to use for map
      * @iova: start address to map
      * @size: size of the range to map
      * @fd: descriptor of the file to map
      * @start: starting file offset of the range to map
      * @readonly: map read only if true
      */

- Steve

>>       /**
>>        * @dma_unmap
>>        *
>