Re: [PATCH 1/2] vfio/container: Support unmap all in one ioctl()

["Cédric Le Goater" <clg@redhat.com>]

On 10/8/25 12:18, Duan, Zhenzhong wrote:
> 
> 
>> -----Original Message-----
>> From: Cédric Le Goater <clg@redhat.com>
>> Subject: Re: [PATCH 1/2] vfio/container: Support unmap all in one ioctl()
>>
>> On 10/1/25 00:04, John Levon wrote:
>>> On Tue, Sep 30, 2025 at 05:26:59PM +0200, Cédric Le Goater wrote:
>>>
>>>>> -        }
>>>>> +        ret = ioctl(container->fd, VFIO_CHECK_EXTENSION,
>> VFIO_UNMAP_ALL);
>>>>
>>>> Could we introduce an helper to test 'unmap_all' support in the host
>>>> kernel ? The result would be something like :
>>>>
>>>>     if (unmap_all) {
>>>>           if
>> (vfio_legacy_has_unmap_all(VFIO_IOMMU_LEGACY(bcontainer))) {
>>>>               flags = VFIO_DMA_UNMAP_FLAG_ALL;
>>>>           } else {
>>>>               /* The unmap ioctl doesn't accept a full 64-bit span. */
>>>>               Int128 llsize = int128_rshift(int128_2_64(), 1);
>>>>               ...
>>>>           }
>>>>     }
>>>
>>> For reference/consideration, the previous approach taken in the vfio-user
>>> series:
>>>
>>>
>> https://lore.kernel.org/qemu-devel/20250219144858.266455-4-john.levon@
>> nutanix.com/
>>>
>>> @@ -533,6 +562,11 @@ static bool vfio_legacy_setup(VFIOContainerBase
>> *bcontainer, Error **errp)
>>>        vfio_get_info_iova_range(info, bcontainer);
>>>
>>>        vfio_get_iommu_info_migration(container, info);
>>> +
>>> +    ret = ioctl(container->fd, VFIO_CHECK_EXTENSION,
>> VFIO_UNMAP_ALL);
>>> +
>>> +    container->unmap_all_supported = (ret != 0);
> 
> Good suggestion, thanks John.
> 
>>>
>>> (I dropped this particular change as part of getting merged.)
>> Yes. I'm reconsidering now.
>>
>> Should we introduce a VFIOContainerBase attribute/flag
>> 'unmap_all_supported',
>> set in the vioc->setup handler ?
> 
> Do you mean to check bcontainer->unmap_all_supported and do the split in vfio_listener_region_del()?
> 
> If only checking it in legacy container, putting it in VFIOLegacyContainer sounds better?

It depends if vfio-user needs it too.

C.