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Thu, 28 May 2026 14:43:58 -0700 Date: Thu, 28 May 2026 14:43:57 -0700 From: Nicolin Chen To: Pranjal Shrivastava CC: , Will Deacon , Joerg Roedel , Robin Murphy , Jason Gunthorpe , Mostafa Saleh , Daniel Mentz , Ashish Mhetre , Subject: Re: [PATCH v7 11/11] iommu/arm-smmu-v3: Add KUnit unit tests for Runtime PM Message-ID: References: <20260527221407.1756491-1-praan@google.com> <20260527221407.1756491-12-praan@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20260527221407.1756491-12-praan@google.com> X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: MW1PEPF0001615B:EE_|SJ1PR12MB6363:EE_ X-MS-Office365-Filtering-Correlation-Id: 0bf46bee-ba95-4a8d-c0e7-08debd02431f X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|30052699003|1800799024|82310400026|36860700016|376014|20052099010|22082099003|18002099003|6133799003|3023799007|11063799006|4143699003|56012099006; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: iBAGddx57ViJHvpxozySh+BTxOWrtaoG+qh5sQkyYYRvYAj0HErCO07rlGJxbzjMR2xuKMQRX7wBtPxAYckkeU+/d+WZfZfiE8SOeJbfw88xsLZAiCUheeqWWB/X9+p+LYFh9G+O1Q9ioC+dzNPsw1eP0cH+iFS+m6QT4lZFg2ZGOnfbilSYl8P2KE/OIaOGX6ytpdpuLLcyHAna1qaRW3Lp2WnK0ANDS4+luBgbaCMkFaxsPDV+fZGtWcvXbrTM25wGpTeGi/4faUrosLTWVvV+oAANXBD4FCY8i8OKAlpCx4JKXV4m5hNlgoJFygXngmKMn9XQ01sdvzOnHhV6N2dh2kA1KWYmZwYrZZYQsMh6tEnKsa+cQEzsd3ql5kreVwCTfXIkfY0jHuf+EVNZ6iPWcSYEtJyMqb1Q7uZk80V39K0yUJPmOWKGV6eMPhXS X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 28 May 2026 21:44:14.5421 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 0bf46bee-ba95-4a8d-c0e7-08debd02431f X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.161];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: MW1PEPF0001615B.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ1PR12MB6363 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260528_144425_199899_686F5394 X-CRM114-Status: GOOD ( 29.97 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, May 27, 2026 at 10:14:07PM +0000, Pranjal Shrivastava wrote: > Introduce a kunit selftests to verify the Runtime PM elision gating, > post-suspend elisions and progress on resumption under active > invalidation load. Simulate concurrent HW suspension using a timer. > Mock all HW registers and CMDQ buffers by allocating them on RAM. > Make the mock CMDQ self-consuming to avoid hitting queue_full scenarios. > > Signed-off-by: Pranjal Shrivastava Maybe I am wrong, yet this reads like an entirely AI-generated code. So, should it have an Assisted-by? Documentation/process/submitting-patches.rst:637:Using Assisted-by: Documentation/process/submitting-patches.rst:641:you need to acknowledge that use by adding an Assisted-by tag. Failure to Documentation/process/coding-assistants.rst:44:Contributions should include an Assisted-by tag in the following format:: Documentation/process/coding-assistants.rst:46: Assisted-by: AGENT_NAME:MODEL_VERSION [TOOL1] [TOOL2] Documentation/process/coding-assistants.rst:59: Assisted-by: Claude:claude-3-opus coccinelle sparse > +struct arm_smmu_test_pm_context { > + u32 *mock_prod_reg; > + u64 *mock_base; > + unsigned long *mock_valid_map; > +}; It seems all about cmdq only, so maybe: struct arm_smmu_mock_cmdq ? > +/* > + * Shared helper to allocate and map a fully functional, self-consuming mock Is it really a "Shared" helper? I see only one caller.. > + * CMDQ. By redirecting both prod_reg and cons_reg to the same memory location, > + * every producer write is instantly reflected as a consumer completion. > + */ > +static struct arm_smmu_test_pm_context * > +arm_smmu_v3_test_init_mock_cmdq(struct kunit *test, struct arm_smmu_device *smmu) > +{ > + struct arm_smmu_test_pm_context *ctx; > + struct arm_smmu_cmdq *cmdq = &smmu->cmdq; > + > + ctx = kunit_kzalloc(test, sizeof(*ctx), GFP_KERNEL); > + KUNIT_ASSERT_NOT_NULL(test, ctx); This ctx struct isn't that large. Maybe the test function (caller) can put on the stack and pass its point int than allocation? > + /* Use a standard 1024-entry queue for safe word bitmask alignment */ > + ctx->mock_prod_reg = kunit_kzalloc(test, sizeof(u32), GFP_KERNEL); Is a u32 allocation necessary? > + ctx->mock_base = kunit_kzalloc(test, 1024 * 16, GFP_KERNEL); s/16/sizeof(struct arm_smmu_cmd) > + ctx->mock_valid_map = kunit_kzalloc(test, BITS_TO_LONGS(1024) * sizeof(long), GFP_KERNEL); > + > + KUNIT_ASSERT_NOT_NULL(test, ctx->mock_prod_reg); > + KUNIT_ASSERT_NOT_NULL(test, ctx->mock_base); > + KUNIT_ASSERT_NOT_NULL(test, ctx->mock_valid_map); > + > + smmu->features = 0; > + /* 1024 entries */ > + cmdq->q.llq.max_n_shift = 10; > + /* SMMUv3 commands are 2 dwords (16 bytes) */ > + cmdq->q.ent_dwords = 2; CMDQ_ENT_DWORDS? > + cmdq->q.base = (__le64 *)ctx->mock_base; ctx->mock_base doesn't seem to have any other use? Why does it have to be in the ctx structure? > + cmdq->valid_map = (atomic_long_t *)ctx->mock_valid_map; Same questions. > + /* Self-Consuming, prod == cons always ensures queue empty */ > + cmdq->q.prod_reg = (__force u32 __iomem *)ctx->mock_prod_reg; > + cmdq->q.cons_reg = (__force u32 __iomem *)ctx->mock_prod_reg; > + > + /* Initialize memory indices */ > + atomic_set(&cmdq->q.llq.atomic.prod, 0); > + atomic_set(&cmdq->q.llq.atomic.cons, 0); > + atomic_set(&cmdq->owner_prod, 0); > + *ctx->mock_prod_reg = 0; Arguably, mock_prod_reg is only used to test against a prod snapshot so it doesn't seem necessary to be in a structure. > + return ctx; > +} > + > +struct arm_smmu_test_timer_context { > + struct kunit *test; > + struct arm_smmu_device *smmu; > + struct arm_smmu_test_pm_context *pm_ctx; pm_ctx doesn't seem to be used by the timer callback function? Is it necessary in this structure? Even "test" isn't used. >. + struct timer_list timer; > + bool stopped; > +}; > + > +/* Asynchronous timer callback running in softirq context */ Would be nicer to replace this with the inline comments: /* Simulate a concurrent runtime suspend event interrupting the invalidations */ > +static void arm_smmu_v3_test_rpm_timer_callback(struct timer_list *t) > +{ > + struct arm_smmu_test_timer_context *ctx = > + timer_container_of(ctx, t, timer); > + struct arm_smmu_cmdq *cmdq = &ctx->smmu->cmdq; > + > + /* > + * Asynchronously set the STOP_FLAG (Close the gate). > + * Simulate a concurrent runtime suspend event interrupting > + * the invalidations happening under active load. > + */ > + atomic_or(CMDQ_PROD_STOP_FLAG, &cmdq->q.llq.atomic.prod); > + > + /* Signal to the main storm loop that suspend has triggered */ > + WRITE_ONCE(ctx->stopped, true); Then, it should be named "suspended". > +} > + > +/* > + * Verify SMMU PM Runtime gating, elision, and post-suspend resumption > + * safety sequentially under active stress. > + */ > +static void arm_smmu_v3_test_rpm_stress_race(struct kunit *test) > +{ > + struct arm_smmu_device *smmu = kunit_kzalloc(test, sizeof(*smmu), GFP_KERNEL); arm-smmu-v3-test has a global arm_smmu_device to use. > + struct arm_smmu_test_pm_context *pm_ctx; > + struct arm_smmu_test_timer_context *timer_ctx; > + struct arm_smmu_cmdq *cmdq = &smmu->cmdq; > + struct arm_smmu_cmd cmd = arm_smmu_make_cmd_cfgi_all(); Can we organize this a bit? Maybe in an inverted xmas tree? Also, it would be nicer to run git-clang-format. > + u32 stopped_prod; > + int i, ret; > + > + KUNIT_ASSERT_NOT_NULL(test, smmu); > + pm_ctx = arm_smmu_v3_test_init_mock_cmdq(test, smmu); > + > + timer_ctx = kunit_kmalloc(test, sizeof(*timer_ctx), GFP_KERNEL); > + KUNIT_ASSERT_NOT_NULL(test, timer_ctx); The allocation doesn't seem necessary either. We use kunit_kzalloc in this file only when the memory (usually an array) is too large. > + timer_ctx->stopped = false; Then, should have been kunit_kzalloc() at least. Or " = {0};", if keep it on the stack. > + /* Setup the kernel software timer */ > + timer_setup(&timer_ctx->timer, arm_smmu_v3_test_rpm_timer_callback, 0); > + > + /* Start the timer to fire in 10 jiffies */ > + mod_timer(&timer_ctx->timer, jiffies + msecs_to_jiffies(10)); Both lines reads pretty clear without that verbose comments... > + > + /* Execute the unmap storm until the timer triggers */ > + while (!READ_ONCE(timer_ctx->stopped)) { > + ret = arm_smmu_cmdq_issue_cmdlist(smmu, cmdq, &cmd, 1, false); > + if (ret != 0) { > + KUNIT_FAIL(test, "Unmap Storm loop failed to submit cmd list: %d\n", ret); > + break; > + } As of now, arm_smmu_cmdq_issue_cmdlist() fails only on -ETIMEDOUT and spits a print already. So, maybe simplify it: if (arm_smmu_cmdq_issue_cmdlist()) break; > static struct kunit_case arm_smmu_v3_test_cases[] = { > + KUNIT_CASE(arm_smmu_v3_test_rpm_stress_race), > KUNIT_CASE(arm_smmu_v3_write_ste_test_bypass_to_abort), > KUNIT_CASE(arm_smmu_v3_write_ste_test_abort_to_bypass), > KUNIT_CASE(arm_smmu_v3_write_ste_test_cdtable_to_abort), Usually we append to the end. And following the naming convention: arm_smmu_v3_rpm_test_stress_race Nicolin