On 3/17/25 6:54 PM, Nicolin Chen wrote:
> On Wed, Mar 12, 2025 at 04:15:10PM +0100, Eric Auger wrote:
>> On 3/11/25 3:10 PM, Shameer Kolothum wrote:
>>> Based on SMMUv3 as a parent device, add a user-creatable smmuv3-accel
>>> device. In order to support vfio-pci dev assignment with a Guest
>> guest
>>> SMMUv3, the physical SMMUv3 has to be configured in nested(S1+s2)
>> nested (s1+s2)
>>> mode, with Guest owning the S1 page tables. Subsequent patches will
>> the guest
>>> add support for smmuv3-accel to provide this.
>> Can't this -accel smmu also works with emulated devices? Do we want an
>> exclusive usage?
> Is there any benefit from emulated devices working in the HW-
> accelerated nested translation mode?
Not really but do we have any justification for using different device
name in accel mode? I am not even sure that accel option is really
needed. Ideally the qemu device should be able to detect it is
protecting a VFIO device, in which case it shall check whether nested is
supported by host SMMU and then automatically turn accel mode?
I gave the example of the vfio device which has different class
implementration depending on the iommufd option being set or not.
Thanks
Eric
>
> Thanks
> Nicolin
>
