kselftest/arm64: Enforce actual ABI for SVE syscalls

Currently syscall-abi permits the bits in Z registers not shared with the
V registers as well as all of the predicate registers to be preserved on
syscall but the actual implementation has always cleared them and our
documentation has now been updated to make that the documented ABI so
update the syscall-abi test to match.
Signed-off-by: Mark Brown <broonie@kernel.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20220829162502.886816-4-broonie@kernel.orgSigned-off-by: Catalin Marinas <catalin.marinas@arm.com>

tools/testing/selftests/arm64/abi/syscall-abi.c

@@ -112,6 +112,8 @@ static int check_fpr(struct syscall_cfg *cfg, int sve_vl, int sme_vl,
 	return errors;
 }
 
+#define SVE_Z_SHARED_BYTES (128 / 8)
+
 static uint8_t z_zero[__SVE_ZREG_SIZE(SVE_VQ_MAX)];
 uint8_t z_in[SVE_NUM_ZREGS * __SVE_ZREG_SIZE(SVE_VQ_MAX)];
 uint8_t z_out[SVE_NUM_ZREGS * __SVE_ZREG_SIZE(SVE_VQ_MAX)];
@@ -133,22 +135,39 @@ static int check_z(struct syscall_cfg *cfg, int sve_vl, int sme_vl,
 	if (!sve_vl)
 		return 0;
 
-	/*
-	 * After a syscall the low 128 bits of the Z registers should
-	 * be preserved and the rest be zeroed or preserved, except if
-	 * we were in streaming mode in which case the low 128 bits may
-	 * also be cleared by the transition out of streaming mode.
-	 */
 	for (i = 0; i < SVE_NUM_ZREGS; i++) {
-		void *in = &z_in[reg_size * i];
-		void *out = &z_out[reg_size * i];
-
-		if ((memcmp(in, out, SVE_VQ_BYTES) != 0) &&
-		    !((svcr & SVCR_SM_MASK) &&
-		      memcmp(z_zero, out, SVE_VQ_BYTES) == 0)) {
-			ksft_print_msg("%s SVE VL %d Z%d low 128 bits changed\n",
-				       cfg->name, sve_vl, i);
-			errors++;
+		uint8_t *in = &z_in[reg_size * i];
+		uint8_t *out = &z_out[reg_size * i];
+
+		if (svcr & SVCR_SM_MASK) {
+			/*
+			 * In streaming mode the whole register should
+			 * be cleared by the transition out of
+			 * streaming mode.
+			 */
+			if (memcmp(z_zero, out, reg_size) != 0) {
+				ksft_print_msg("%s SVE VL %d Z%d non-zero\n",
+					       cfg->name, sve_vl, i);
+				errors++;
+			}
+		} else {
+			/*
+			 * For standard SVE the low 128 bits should be
+			 * preserved and any additional bits cleared.
+			 */
+			if (memcmp(in, out, SVE_Z_SHARED_BYTES) != 0) {
+				ksft_print_msg("%s SVE VL %d Z%d low 128 bits changed\n",
+					       cfg->name, sve_vl, i);
+				errors++;
+			}
+
+			if (reg_size > SVE_Z_SHARED_BYTES &&
+			    (memcmp(z_zero, out + SVE_Z_SHARED_BYTES,
+				    reg_size - SVE_Z_SHARED_BYTES) != 0)) {
+				ksft_print_msg("%s SVE VL %d Z%d high bits non-zero\n",
+					       cfg->name, sve_vl, i);
+				errors++;
+			}
 		}
 	}
 
@@ -176,9 +195,9 @@ static int check_p(struct syscall_cfg *cfg, int sve_vl, int sme_vl,
 	if (!sve_vl)
 		return 0;
 
-	/* After a syscall the P registers should be preserved or zeroed */
+	/* After a syscall the P registers should be zeroed */
 	for (i = 0; i < SVE_NUM_PREGS * reg_size; i++)
-		if (p_out[i] && (p_in[i] != p_out[i]))
+		if (p_out[i])
 			errors++;
 	if (errors)
 		ksft_print_msg("%s SVE VL %d predicate registers non-zero\n",
@@ -226,9 +245,9 @@ static int check_ffr(struct syscall_cfg *cfg, int sve_vl, int sme_vl,
 	    !(getauxval(AT_HWCAP2) & HWCAP2_SME_FA64))
 		return 0;
 
-	/* After a syscall the P registers should be preserved or zeroed */
+	/* After a syscall FFR should be zeroed */
 	for (i = 0; i < reg_size; i++)
-		if (ffr_out[i] && (ffr_in[i] != ffr_out[i]))
+		if (ffr_out[i])
 			errors++;
 	if (errors)
 		ksft_print_msg("%s SVE VL %d FFR non-zero\n",