[PATCH 4/4] arm64: KVM: Handle Set/Way CMOs as NOPs if FWB is present

[Marc Zyngier]

Set/Way handling is one of the ugliest corners of KVM. We shouldn't
have to handle that, but better safe than sorry.

Thankfully, FWB fixes this for us by not requiering any maintenance
whatsoever, which means we don't have to emulate S/W CMOs, and don't
have to track VM ops either.

We still have to trap S/W though, if only to prevent the guest from
doing something bad.

Signed-off-by: Marc Zyngier <marc.zyngier at arm.com>
---
 arch/arm64/kvm/sys_regs.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 806b0b126a64..ef373963bf95 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -195,7 +195,13 @@ static bool access_dcsw(struct kvm_vcpu *vcpu,
 	if (!p->is_write)
 		return read_from_write_only(vcpu, p, r);
 
-	kvm_set_way_flush(vcpu);
+	/*
+	 * Only track S/W ops if we don't have FWB. It still indicates
+	 * that the guest is a bit broken...
+	 */
+	if (!cpus_have_const_cap(ARM64_HAS_STAGE2_FWB))
+		kvm_set_way_flush(vcpu);
+
 	return true;
 }
 
-- 
2.14.2