The HCR_EL2.TSC trap for trapping EL1 execution of SMC instructions
has a behaviour change for FEAT_NV when EL3 is not implemented:
* in older architecture versions TSC was required to have no
effect (i.e. the SMC insn UNDEFs)
* with FEAT_NV, when HCR_EL2.NV == 1 the trap must apply
(i.e. SMC traps to EL2, as it already does in all cases when
EL3 is implemented)
* in newer architecture versions, the behaviour either without
FEAT_NV or with FEAT_NV and HCR_EL2.NV == 0 is relaxed to
an IMPDEF choice between UNDEF and trap-to-EL2 (i.e. it is
permitted to always honour HCR_EL2.TSC) for AArch64 only
Add the condition to honour the trap bit when HCR_EL2.NV == 1. We
leave the HCR_EL2.NV == 0 case with the existing (UNDEF) behaviour,
as our IMPDEF choice (both because it avoids a behaviour change
for older CPU models and because we'd have to distinguish AArch32
from AArch64 if we opted to trap to EL2).
Signed-off-by: Peter Maydell <peter.mayd...@linaro.org>
---
target/arm/tcg/op_helper.c | 16 +++++++++++++---
1 file changed, 13 insertions(+), 3 deletions(-)
diff --git a/target/arm/tcg/op_helper.c b/target/arm/tcg/op_helper.c
index ea08936a852..ae158200c00 100644
--- a/target/arm/tcg/op_helper.c
+++ b/target/arm/tcg/op_helper.c
@@ -930,7 +930,14 @@ void HELPER(pre_smc)(CPUARMState *env, uint32_t syndrome)
*
* Conduit SMC, valid call Trap to EL2 PSCI Call
* Conduit SMC, inval call Trap to EL2 Undef insn
- * Conduit not SMC Undef insn Undef insn
+ * Conduit not SMC Undef or trap[1] Undef insn
+ *
+ * [1] In this case:
+ * - if HCR_EL2.NV == 1 we must trap to EL2
+ * - if HCR_EL2.NV == 0 then newer architecture revisions permit
+ * AArch64 (but not AArch32) to trap to EL2 as an IMPDEF choice
+ * - otherwise we must UNDEF
+ * We take the IMPDEF choice to always UNDEF if HCR_EL2.NV == 0.
*/
/* On ARMv8 with EL3 AArch64, SMD applies to both S and NS state.
@@ -944,9 +951,12 @@ void HELPER(pre_smc)(CPUARMState *env, uint32_t syndrome)
: smd_flag && !secure;
if (!arm_feature(env, ARM_FEATURE_EL3) &&
+ !(arm_hcr_el2_eff(env) & HCR_NV) &&
cpu->psci_conduit != QEMU_PSCI_CONDUIT_SMC) {
- /* If we have no EL3 then SMC always UNDEFs and can't be
- * trapped to EL2. PSCI-via-SMC is a sort of ersatz EL3
+ /*
+ * If we have no EL3 then traditionally SMC always UNDEFs and can't be
+ * trapped to EL2. For nested virtualization, SMC can be trapped to
+ * the outer hypervisor. PSCI-via-SMC is a sort of ersatz EL3
* firmware within QEMU, and we want an EL2 guest to be able
* to forbid its EL1 from making PSCI calls into QEMU's
* "firmware" via HCR.TSC, so for these purposes treat
--
2.34.1
