From: Jacob Pan <jacob.pan@linux.microsoft.com>
To: linux-kernel@vger.kernel.org,
"iommu@lists.linux.dev" <iommu@lists.linux.dev>,
Will Deacon <will@kernel.org>, Joerg Roedel <joro@8bytes.org>,
Mostafa Saleh <smostafa@google.com>,
Jason Gunthorpe <jgg@nvidia.com>,
Robin Murphy <robin.murphy@arm.com>,
Nicolin Chen <nicolinc@nvidia.com>
Cc: Jacob Pan <jacob.pan@linux.microsoft.com>,
Zhang Yu <zhangyu1@linux.microsoft.com>,
Jean Philippe-Brucker <jean-philippe@linaro.org>,
Alexander Grest <Alexander.Grest@microsoft.com>
Subject: [PATCH v5 1/3] iommu/arm-smmu-v3: Parameterize wfe for CMDQ polling
Date: Mon, 8 Dec 2025 13:28:55 -0800 [thread overview]
Message-ID: <20251208212857.13101-2-jacob.pan@linux.microsoft.com> (raw)
In-Reply-To: <20251208212857.13101-1-jacob.pan@linux.microsoft.com>
When SMMU_IDR0.SEV == 1, the SMMU triggers a WFE wake-up event when a
Command queue becomes non-full and an agent external to the SMMU could
have observed that the queue was previously full. However, WFE is not
always required or available during space polling. Introduce an optional
parameter to control WFE usage.
Signed-off-by: Jacob Pan <jacob.pan@linux.microsoft.com>
---
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index bf67d9abc901..d637a5dcf48a 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -191,11 +191,11 @@ static u32 queue_inc_prod_n(struct arm_smmu_ll_queue *q, int n)
}
static void queue_poll_init(struct arm_smmu_device *smmu,
- struct arm_smmu_queue_poll *qp)
+ struct arm_smmu_queue_poll *qp, bool want_wfe)
{
qp->delay = 1;
qp->spin_cnt = 0;
- qp->wfe = !!(smmu->features & ARM_SMMU_FEAT_SEV);
+ qp->wfe = want_wfe && (!!(smmu->features & ARM_SMMU_FEAT_SEV));
qp->timeout = ktime_add_us(ktime_get(), ARM_SMMU_POLL_TIMEOUT_US);
}
@@ -656,13 +656,11 @@ static int __arm_smmu_cmdq_poll_until_msi(struct arm_smmu_device *smmu,
struct arm_smmu_queue_poll qp;
u32 *cmd = (u32 *)(Q_ENT(&cmdq->q, llq->prod));
- queue_poll_init(smmu, &qp);
-
/*
* The MSI won't generate an event, since it's being written back
* into the command queue.
*/
- qp.wfe = false;
+ queue_poll_init(smmu, &qp, false);
smp_cond_load_relaxed(cmd, !VAL || (ret = queue_poll(&qp)));
llq->cons = ret ? llq->prod : queue_inc_prod_n(llq, 1);
return ret;
@@ -680,7 +678,7 @@ static int __arm_smmu_cmdq_poll_until_consumed(struct arm_smmu_device *smmu,
u32 prod = llq->prod;
int ret = 0;
- queue_poll_init(smmu, &qp);
+ queue_poll_init(smmu, &qp, true);
llq->val = READ_ONCE(cmdq->q.llq.val);
do {
if (queue_consumed(llq, prod))
--
2.43.0
next prev parent reply other threads:[~2025-12-08 21:29 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-12-08 21:28 [PATCH v5 0/3] SMMU v3 CMDQ fix and improvement Jacob Pan
2025-12-08 21:28 ` Jacob Pan [this message]
2025-12-08 21:28 ` [PATCH v5 2/3] iommu/arm-smmu-v3: Fix CMDQ timeout warning Jacob Pan
2025-12-10 3:16 ` Will Deacon
2025-12-12 20:05 ` Jacob Pan
2025-12-08 21:28 ` [PATCH v5 3/3] iommu/arm-smmu-v3: Improve CMDQ lock fairness and efficiency Jacob Pan
2026-01-05 22:58 ` [PATCH v5 0/3] SMMU v3 CMDQ fix and improvement Will Deacon
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