[PATCH 10/11] KVM: arm64: nv: Honor guest hypervisor's FP/SVE traps in CPTR_EL2

[Oliver Upton <oliver.upton@linux.dev>]

Start folding the guest hypervisor's FP/SVE traps into the value
programmed in hardware. Note that as of writing this is dead code, since
KVM does a full put() / load() for every nested exception boundary which
saves + flushes the FP/SVE state.

However, this will become useful when we can keep the guest's FP/SVE
state alive across a nested exception boundary and the host no longer
needs to conservatively program traps.

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
---
 arch/arm64/kvm/hyp/vhe/switch.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/arch/arm64/kvm/hyp/vhe/switch.c b/arch/arm64/kvm/hyp/vhe/switch.c
index 697253673d7b..d07b4f4be5e5 100644
--- a/arch/arm64/kvm/hyp/vhe/switch.c
+++ b/arch/arm64/kvm/hyp/vhe/switch.c
@@ -85,6 +85,19 @@ static void __activate_cptr_traps(struct kvm_vcpu *vcpu)
 		__activate_traps_fpsimd32(vcpu);
 	}
 
+	/*
+	 * Layer the guest hypervisor's trap configuration on top of our own if
+	 * we're in a nested context.
+	 */
+	if (!vcpu_has_nv(vcpu) || is_hyp_ctxt(vcpu))
+		goto write;
+
+	if (guest_hyp_fpsimd_traps_enabled(vcpu))
+		val &= ~CPACR_ELx_FPEN;
+	if (guest_hyp_sve_traps_enabled(vcpu))
+		val &= ~CPACR_ELx_ZEN;
+
+write:
 	write_sysreg(val, cpacr_el1);
 }
 
-- 
2.45.1.288.g0e0cd299f1-goog