[PATCH v2 3/3] KVM: selftests: arm64: Skip sea_to_user when EINJ places no poison

[Like Xu]

sea_to_user injects a memory UER with EINJ notrigger=1 and expects the
guest to consume it and trap to KVM as an SEA. On some firmware the test
aborts instead:

  arm64/sea_to_user.c:223: exit_reason == (41)
  Wanted KVM exit reason: 41 (ARM_SEA), got: 6 (MMIO)

notrigger=1 asks firmware to arm the poison without consuming it, but on
these platforms the poison is only armed as part of the trigger step that
notrigger skips, so nothing consumable is left in memory. The guest reads
back the sentinel, no SEA occurs, and GUEST_FAIL fires. On arm64 a ucall
is delivered as an MMIO write, which surfaces as the KVM_EXIT_MMIO above
rather than a KVM bug.

The file already documents that the test must be skipped when firmware
cannot deliver a consumable error. Detect the guest abort that follows a
missing SEA and skip, instead of failing on a firmware limitation the
test cannot control.

Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Like Xu <likexu@xxxxxxxxxxx>
---
 .../testing/selftests/kvm/arm64/sea_to_user.c | 24 +++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/kvm/arm64/sea_to_user.c b/tools/testing/selftests/kvm/arm64/sea_to_user.c
index 7cf95da8e594d..d4af6e0eed288 100644
--- a/tools/testing/selftests/kvm/arm64/sea_to_user.c
+++ b/tools/testing/selftests/kvm/arm64/sea_to_user.c
@@ -215,13 +215,33 @@ static void run_vm(struct kvm_vm *vm, struct kvm_vcpu *vcpu)
 
 	ksft_print_msg("Dump kvm_run info about KVM_EXIT_%s\n",
 		       exit_reason_str(run->exit_reason));
+
+	/*
+	 * The guest's read of the injected location is expected to trap to KVM
+	 * as an SEA. If it does not, the injected error was never placed as
+	 * consumable poison: some firmware honours EINJ's notrigger request by
+	 * arming the poison only as part of the (now skipped) trigger step, so
+	 * nothing is left in memory for the guest to consume. The guest then
+	 * reads back the sentinel value and reports it via GUEST_FAIL, which
+	 * arm64 delivers as a ucall over MMIO (hence a KVM_EXIT_MMIO here).
+	 * Treat that as "this platform cannot host the test" and skip, matching
+	 * the requirement documented at the top of this file, rather than
+	 * failing on a hardware/firmware limitation the test cannot control.
+	 */
+	if (run->exit_reason != KVM_EXIT_ARM_SEA &&
+	    get_ucall(vcpu, &uc) == UCALL_ABORT) {
+		ksft_print_msg("Guest consumed no SEA: %s", uc.buffer);
+		ksft_exit_skip("EINJ notrigger placed no consumable poison on this platform\n");
+	}
+
+	TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_ARM_SEA);
+
+	/* arm_sea holds valid data only for a KVM_EXIT_ARM_SEA exit. */
 	ksft_print_msg("kvm_run.arm_sea: esr=%#llx, flags=%#llx\n",
 		       run->arm_sea.esr, run->arm_sea.flags);
 	ksft_print_msg("kvm_run.arm_sea: gva=%#llx, gpa=%#llx\n",
 		       run->arm_sea.gva, run->arm_sea.gpa);
 
-	TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_ARM_SEA);
-
 	esr = run->arm_sea.esr;
 	TEST_ASSERT_EQ(ESR_ELx_EC(esr), ESR_ELx_EC_DABT_LOW);
 	TEST_ASSERT_EQ(esr & ESR_ELx_FSC_TYPE, ESR_ELx_FSC_EXTABT);
-- 
2.50.1 (Apple Git-155)