Re: [RFC PATCH v1 0/8] Arm Core Local Accelerator Driver

[Ryan Roberts]

On 17/07/2026 14:32, Jason Gunthorpe wrote:
> On Fri, Jul 17, 2026 at 12:33:17PM +0100, Will Deacon wrote:
> 
>> first. So, at the moment, this just looks like a burden to me, especially
>> as it appears to create a brand new, device-specific UAPI for what is
>> ostensibly a form of SVA - something which the community is actively
>> working on already.
> 
> Yeah, I think it was a mistake to hardwire the invalidation to the
> CPU. It would fit much better into Linux if the invalidation was
> separate and independently controllable with an option to follow the
> CPU.

Well I'm certainly not going to disagree, but the HW is somewhat fixed at this
point :-|

> 
> Then you could use a normal S2 page table through iommufd and not mess
> with kvm. (though the VMID sharing with KVM for a BTM-like scheme was
> never solved upstream)
> 
> I also wouldn't expect you to use vfio-mdev, if the devices are
> discovered and known at boot then it should be a normal vfio driver.

OK good feedback - I'm not going to claim to be a VFIO expert (especially not in
front of an actual VFIO expert) - We'll look closer at this and come back if we
have questions (although unlikely over the summer holiday).

Thanks,
Ryan


> 
> Jason