linux-kernel - Re: [PATCH rc v4 4/4] iommu/arm-smmu-v3-test: Add nested s1bypass/s1dssbypass coverage

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Message-ID: <aUQwKot1Ao0lE-C1@google.com>
Date: Thu, 18 Dec 2025 16:47:38 +0000
From: Mostafa Saleh <smostafa@...gle.com>
To: Nicolin Chen <nicolinc@...dia.com>
Cc: jgg@...dia.com, will@...nel.org, robin.murphy@....com, joro@...tes.org,
	linux-arm-kernel@...ts.infradead.org, iommu@...ts.linux.dev,
	linux-kernel@...r.kernel.org, skolothumtho@...dia.com,
	praan@...gle.com, xueshuai@...ux.alibaba.com
Subject: Re: [PATCH rc v4 4/4] iommu/arm-smmu-v3-test: Add nested
 s1bypass/s1dssbypass coverage

On Tue, Dec 16, 2025 at 08:26:02PM -0800, Nicolin Chen wrote:
> STE in a nested case requires both S1 and S2 fields. And this makes the use
> case different from the existing one.
> 
> Add coverage for previously failed cases shifting between S2-only and S1+S2
> STEs.
> 
> Reviewed-by: Shuai Xue <xueshuai@...ux.alibaba.com>
> Signed-off-by: Nicolin Chen <nicolinc@...dia.com>
> ---
>  .../iommu/arm/arm-smmu-v3/arm-smmu-v3-test.c  | 46 +++++++++++++++++++
>  1 file changed, 46 insertions(+)
> 
> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-test.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-test.c
> index 5db14718fdd6..8255a02f4efa 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-test.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-test.c
> @@ -33,8 +33,12 @@ static struct mm_struct sva_mm = {
>  enum arm_smmu_test_master_feat {
>  	ARM_SMMU_MASTER_TEST_ATS = BIT(0),
>  	ARM_SMMU_MASTER_TEST_STALL = BIT(1),
> +	ARM_SMMU_MASTER_TEST_NESTED = BIT(2),
>  };
>  
> +static void arm_smmu_test_make_s2_ste(struct arm_smmu_ste *ste,
> +				      enum arm_smmu_test_master_feat feat);
> +
>  static bool arm_smmu_entry_differs_in_used_bits(const __le64 *entry,
>  						const __le64 *used_bits,
>  						const __le64 *target,
> @@ -197,6 +201,17 @@ static void arm_smmu_test_make_cdtable_ste(struct arm_smmu_ste *ste,
>  	};
>  
>  	arm_smmu_make_cdtable_ste(ste, &master, ats_enabled, s1dss);
> +	if (feat & ARM_SMMU_MASTER_TEST_NESTED) {
> +		struct arm_smmu_ste s2ste;
> +		int i;
> +
> +		arm_smmu_test_make_s2_ste(&s2ste, ARM_SMMU_MASTER_TEST_ATS);

Shouldn't that be conditional on "ats_enabled", I see the callers of the
new tests already set ARM_SMMU_MASTER_TEST_ATS.

Thanks,
Mostafa

> +		ste->data[0] |= cpu_to_le64(
> +			FIELD_PREP(STRTAB_STE_0_CFG, STRTAB_STE_0_CFG_NESTED));
> +		ste->data[1] |= cpu_to_le64(STRTAB_STE_1_MEV);
> +		for (i = 2; i < NUM_ENTRY_QWORDS; i++)
> +			ste->data[i] = s2ste.data[i];
> +	}
>  }
>  
>  static void arm_smmu_v3_write_ste_test_bypass_to_abort(struct kunit *test)
> @@ -554,6 +569,35 @@ static void arm_smmu_v3_write_ste_test_s2_to_s1_stall(struct kunit *test)
>  						       NUM_EXPECTED_SYNCS(3));
>  }
>  
> +static void
> +arm_smmu_v3_write_ste_test_nested_s1dssbypass_to_s1bypass(struct kunit *test)
> +{
> +	struct arm_smmu_ste s1_ste;
> +	struct arm_smmu_ste s2_ste;
> +
> +	arm_smmu_test_make_cdtable_ste(
> +		&s1_ste, STRTAB_STE_1_S1DSS_BYPASS, fake_cdtab_dma_addr,
> +		ARM_SMMU_MASTER_TEST_ATS | ARM_SMMU_MASTER_TEST_NESTED);
> +	arm_smmu_test_make_s2_ste(&s2_ste, 0);
> +	/* Expect an additional sync to unset ignored bits: EATS and MEV */
> +	arm_smmu_v3_test_ste_expect_hitless_transition(test, &s1_ste, &s2_ste,
> +						       NUM_EXPECTED_SYNCS(3));
> +}
> +
> +static void
> +arm_smmu_v3_write_ste_test_nested_s1bypass_to_s1dssbypass(struct kunit *test)
> +{
> +	struct arm_smmu_ste s1_ste;
> +	struct arm_smmu_ste s2_ste;
> +
> +	arm_smmu_test_make_cdtable_ste(
> +		&s1_ste, STRTAB_STE_1_S1DSS_BYPASS, fake_cdtab_dma_addr,
> +		ARM_SMMU_MASTER_TEST_ATS | ARM_SMMU_MASTER_TEST_NESTED);
> +	arm_smmu_test_make_s2_ste(&s2_ste, 0);
> +	arm_smmu_v3_test_ste_expect_hitless_transition(test, &s2_ste, &s1_ste,
> +						       NUM_EXPECTED_SYNCS(2));
> +}
> +
>  static void arm_smmu_v3_write_cd_test_sva_clear(struct kunit *test)
>  {
>  	struct arm_smmu_cd cd = {};
> @@ -600,6 +644,8 @@ static struct kunit_case arm_smmu_v3_test_cases[] = {
>  	KUNIT_CASE(arm_smmu_v3_write_cd_test_s1_change_asid),
>  	KUNIT_CASE(arm_smmu_v3_write_ste_test_s1_to_s2_stall),
>  	KUNIT_CASE(arm_smmu_v3_write_ste_test_s2_to_s1_stall),
> +	KUNIT_CASE(arm_smmu_v3_write_ste_test_nested_s1dssbypass_to_s1bypass),
> +	KUNIT_CASE(arm_smmu_v3_write_ste_test_nested_s1bypass_to_s1dssbypass),
>  	KUNIT_CASE(arm_smmu_v3_write_cd_test_sva_clear),
>  	KUNIT_CASE(arm_smmu_v3_write_cd_test_sva_release),
>  	{},
> -- 
> 2.43.0
>