KVM: arm64: Optimize protected mode with FWB and DIC

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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@google.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Fuad Tabba <fuad.tabba@linux.dev>
Link: https://patch.msgid.link/20260723162002.3848054-1-smostafa@google.com
Signed-off-by: Oliver Upton <oupton@kernel.org>

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Mostafa Saleh 2026-07-23 16:20:02 +00:00 • committed by Oliver Upton

parent 596289fe48

commit 81b2d03f8c

1 changed files with 7 additions and 0 deletions

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arch/arm64/kvm/hyp/nvhe/mem_protect.c

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