Re: [PATCH v4 09/29] KVM: arm64: use `at s1e1a` for POE

FEAT_ATS1E1A introduces a new instruction: `at s1e1a`.
This is an address translation, without permission checks.

POE allows read permissions to be removed from S1 by the guest.  This means
that an `at` instruction could fail, and not get the IPA.

Switch to using `at s1e1a` so that KVM can get the IPA regardless of S1
permissions.

Signed-off-by: Joey Gouly <joey.gouly@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Oliver Upton <redacted>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
---
 arch/arm64/kvm/hyp/include/hyp/fault.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/hyp/include/hyp/fault.h b/arch/arm64/kvm/hyp/include/hyp/fault.h
index 487c06099d6f..17df94570f03 100644
--- a/arch/arm64/kvm/hyp/include/hyp/fault.h
+++ b/arch/arm64/kvm/hyp/include/hyp/fault.h

@@ -14,6 +14,7 @@
 
 static inline bool __translate_far_to_hpfar(u64 far, u64 *hpfar)
 {
+	int ret;
 	u64 par, tmp;
 
 	/*

@@ -27,7 +28,9 @@ static inline bool __translate_far_to_hpfar(u64 far, u64 *hpfar)
 	 * saved the guest context yet, and we may return early...
 	 */
 	par = read_sysreg_par();
-	if (!__kvm_at(OP_AT_S1E1R, far))
+	ret = system_supports_poe() ? __kvm_at(OP_AT_S1E1A, far) :
+	                              __kvm_at(OP_AT_S1E1R, far);
+	if (!ret)
 		tmp = read_sysreg_par();
 	else
 		tmp = SYS_PAR_EL1_F; /* back to the guest */