[RFC 00/12] arm64: Add support for TLBI domains

[Kristina Martšenko]

On Mon, Oct 19, 2026 at 04:52:04PM +0800, Jinqian Yang wrote:
> Hi,
> 
> On 2026/10/1 19:06, Kristina Martšenko wrote:
> > Hi,
> > 
> > This series allows the kernel to use TLBI domains. TLBI domains (FEAT_TLBID) is
> > an Arm architecture feature that enables a TLB invalidation to target a subset
> > of CPUs instead of the whole system. It can improve performance on systems with
> > many CPUs. TLBID is not yet part of the Arm Architecture Reference Manual but
> > some of it is described in the latest XML [1].
> > 
> > The goal of this series is to send TLBI commands only to the CPUs where a
> > process has run (i.e. where its page tables have been installed). The last
> > patch explains a bit about how it works. This is an RFC since I'm not familiar
> > with the kernel's TLB/mm code and I'd like feedback on whether the general
> > approach is correct.
> > 
> 
> Thanks for posting this series.
> 
> I'm working on the KVM side of TLBID, and have a series that
> virtualizes TLBI domains for guests. It includes:
> 
>  - per-vCPU vDomain configuration via a new capability and
>    two ioctls
>  - VTLBID_EL2 programming at vCPU load/put, mapping vDomains
>    to physical domains
>  - a guest visible TLBIDIDR_EL1 with virtual domain counts,
>    and conditional exposure of ID_AA64MMFR4_EL1.TLBID
> 
> You mentioned you planned to look at KVM support in your next
> version. Would it be OK for us to post this as an RFC on top
> of your series? :)

Thanks for sharing.

I’m starting to look at KVM support but I’m not working on exposing
domains to guests. I’m looking at if we can track which CPUs a guest has
run on and transparently redirect all of a guest’s TLBIs to a single
domain that contains those CPUs. This could be a fallback in case the
guest is not configured to have virtual domains itself (which your
series enables).

I think there is some overlap between what we’re doing (e.g. configuring
VTLBID), but also lots of separate parts. So no objection from my side,
please feel free to post your series.

Thanks,
Kristina