Re: [PATCH v19 09/20] KVM: arm64: Add VM specific callback for S2 MMU operations

[Suzuki K Poulose]

On 28/09/2026 02:25, Gavin Shan wrote:
> On 9/28/26 11:09 AM, Gavin Shan wrote:
> > On 9/21/26 7:28 AM, Suzuki K Poulose wrote:
> > > Add VM type specific S2 MMU operation backends which can be 
> > > initialized per
> > > VM flavor, to keep the handling cleaner.
> > >
> > > Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> > > ---
> > >   arch/arm64/include/asm/kvm_host.h |  15 ++++
> > >   arch/arm64/kvm/mmu.c              | 137 +++++++++++++++++++++++++-----
> > >   2 files changed, 131 insertions(+), 21 deletions(-)

...

> > > +int kvm_arch_flush_remote_tlbs_range(struct kvm *kvm,
> > > +                     gfn_t gfn, u64 nr_pages)
> > > +{
> > > +    if (!kvm->arch.vm_s2_ops->vm_flush_remote_tlbs_range)
> > > +        return 1;
> > > +
> >
> > Realm would the only case where vm_s2_ops->vm_flush_remote_{tlbs, 
> > tlbs_range)
> > are NULL. On request to flush remote TLBs by 
> > kvm_flush_remote_tlbs_range(), it
> > ends up with event KVM_REQ_TLB_FLUSH queued for each vCPU. How this 
> > queued event
> > is linked to a remote TLB flush for realm? The problem is TLBs are 
> > owned by EL2
> > realm and there are no RMI calls for the management. So I'm wandering 
> > we should
> > return 0 here?
>
> vm_s2_ops->vm_flush_remote_{tlbs, tlbs_range} are added in PATCH[14] 
> where 0 is
> returned for both function. So I guess needn't this check at all?
>
>       if (!kvm->arch.vm_s2_ops->vm_flush_remote_tlbs_range)

I would leave that check as they are. The only callback that
is mandatory is the vm_mem_abort and we do enforce it at init.

Cheers
Suzuki