[PATCH v1 05/10] KVM: arm64: selftests: Test AT S12E1R with an invalid VTCR_EL2.SL0

[Fuad Tabba <fuad.tabba@linux.dev>]

Check that AT S12E1R with SL0 set to 3 on 4K pages, an invalid starting
level without FEAT_TTST (which KVM doesn't expose to an L1 guest),
reports a stage-2 level 0 Translation fault in PAR_EL1. KVM used to
retry the AT forever instead, so without the fix the test hangs. An out
of range T0SZ isn't tested, since the architecture lets an
implementation clamp it instead.

Assisted-by: LLM
Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
---
 tools/testing/selftests/kvm/arm64/at.c | 28 ++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/tools/testing/selftests/kvm/arm64/at.c b/tools/testing/selftests/kvm/arm64/at.c
index ce5d312ef6baa..61fd217f724bd 100644
--- a/tools/testing/selftests/kvm/arm64/at.c
+++ b/tools/testing/selftests/kvm/arm64/at.c
@@ -73,12 +73,40 @@ static void test_at(bool expect_fault)
 	test_at_insn(S1E1W, expect_fault);
 }
 
+/* 4K granule with SL0 == 3 and no FEAT_TTST is a stage-2 level 0 Translation fault */
+static void test_at_s12_bad_sl0(void)
+{
+	u64 vtcr = FIELD_PREP(VTCR_EL2_SL0_MASK, 3) | FIELD_PREP(VTCR_EL2_T0SZ_MASK, 24);
+	u64 sctlr = read_sysreg_s(SYS_SCTLR_EL12);
+	u64 par;
+
+	/* Disable stage 1, so the stage-2 fault is on the output address, not a table walk */
+	write_sysreg_s(sctlr & ~SCTLR_ELx_M, SYS_SCTLR_EL12);
+	write_sysreg(vtcr, vtcr_el2);
+	sysreg_clear_set(hcr_el2, 0, HCR_EL2_VM);
+	isb();
+
+	__at(OP_AT_S12E1R, TEST_ADDR);
+	isb();
+	par = read_sysreg(par_el1);
+
+	sysreg_clear_set(hcr_el2, HCR_EL2_VM, 0);
+	write_sysreg(0, vtcr_el2);
+	write_sysreg_s(sctlr, SYS_SCTLR_EL12);
+	isb();
+
+	__GUEST_ASSERT((par & SYS_PAR_EL1_F) && (par & SYS_PAR_EL1_S) &&
+		       FIELD_GET(SYS_PAR_EL1_FST, par) == ESR_ELx_FSC_FAULT_L(0),
+		       "AT S12E1R: expected stage-2 level 0 translation fault (par: %lx)", par);
+}
+
 static void guest_code(void)
 {
 	sysreg_clear_set(tcr_el1, TCR_HA, 0);
 	isb();
 
 	test_at(true);
+	test_at_s12_bad_sl0();
 
 	if (!SYS_FIELD_GET(ID_AA64MMFR1_EL1, HAFDBS, read_sysreg(id_aa64mmfr1_el1)))
 		GUEST_DONE();
-- 
2.39.5