Re: [PATCH v3] KVM: arm64: Optimize protected mode with FWB and DIC

[Marc Zyngier]

On Thu, 23 Jul 2026 17:20:02 +0100,
Mostafa Saleh <smostafa@xxxxxxxxxx> wrote:
> 
> KVM opportunistically enables FWB if supported by the system for guest
> VMs, which allows it to elude cache maintenance for data as they are
> forced to be cacheable from stage-2.
> In that case, __clean_dcache_guest_page() will immediately return.
> However in protected mode, before calling __clean_dcache_guest_page()
> it loops over the range and fix_map/unmap it, issuing TLB
> invalidations, dsb() and isb() unnecessarily.
> 
> This can be optimized by returning early if FWB is supported,
> kvm_pgtable_stage2_map() already issues dsb() and tlb invalidation
> functions issue dsb() for the unmap path.
> 
> Similarly for DIC, we can omit the call in
> invalidate_icache_guest_page()
> 
> No isb() needed as ERET is context synchronization event.
> 
> Signed-off-by: Mostafa Saleh <smostafa@xxxxxxxxxx>

Acked-by: Marc Zyngier <maz@xxxxxxxxxx>

	M.

-- 
Without deviation from the norm, progress is not possible.