linux-kernel - [PATCH V3 0/2] iommu/arm-smmu-v3: Add support for ECMDQ register mode

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Message-ID: <20240425143013.52292-1-tanmay@marvell.com>
Date: Thu, 25 Apr 2024 07:30:13 -0700
From: Tanmay Jagdale <tanmay@...vell.com>
To: <will@...nel.org>, <robin.murphy@....com>, <joro@...tes.org>,
        <nicolinc@...dia.com>, <mshavit@...gle.com>,
        <baolu.lu@...ux.intel.com>, <thunder.leizhen@...wei.com>,
        <set_pte_at@...look.com>, <smostafa@...gle.com>
CC: <sgoutham@...vell.com>, <gcherian@...vell.com>, <jcm@...masters.org>,
        <linux-arm-kernel@...ts.infradead.org>, <iommu@...ts.linux.dev>,
        <linux-kernel@...r.kernel.org>, Tanmay Jagdale <tanmay@...vell.com>
Subject: [PATCH V3 0/2] iommu/arm-smmu-v3: Add support for ECMDQ register mode 

Resending the patches by Zhen Lei <thunder.leizhen@...wei.com> that add
support for SMMU ECMDQ feature.

Tested this feature on a Marvell SoC by implementing a smmu-test driver.
This test driver spawns a thread per CPU and each thread keeps sending
map, table-walk and unmap requests for a fixed duration.

Using this test driver, we compared ECMDQ vs SMMU with software batching
support and saw ~5% improvement with ECMDQ. Performance numbers are
mentioned below:

                   Total Requests  Average Requests  Difference
                                      Per CPU         wrt ECMDQ
-----------------------------------------------------------------
ECMDQ                 239286381       2991079
CMDQ Batch Size 1     228232187       2852902         -4.62%
CMDQ Batch Size 32    233465784       2918322         -2.43%
CMDQ Batch Size 64    231679588       2895994         -3.18%
CMDQ Batch Size 128   233189030       2914862         -2.55%
CMDQ Batch Size 256   230965773       2887072         -3.48%


v2 --> v3:
1. Rebased on linux 6.9-rc5

v1 --> v2:
1. Drop patch "iommu/arm-smmu-v3: Add arm_smmu_ecmdq_issue_cmdlist() for
non-shared ECMDQ" in v1
2. Drop patch "iommu/arm-smmu-v3: Add support for less than one ECMDQ
per core" in v1
3. Replace rwlock with IPI to support lockless protection against the
write operation to bit
   'ERRACK' during error handling and the read operation to bit 'ERRACK'
during command insertion. 
4. Standardize variable names.
-	struct arm_smmu_ecmdq *__percpu	*ecmdq;
+	struct arm_smmu_ecmdq *__percpu	*ecmdqs;

5. Add member 'iobase' to struct arm_smmu_device to record the start
physical
   address of the SMMU, to replace translation operation
(vmalloc_to_pfn(smmu->base) << PAGE_SHIFT)
+	phys_addr_t			iobase;
-	smmu_dma_base = (vmalloc_to_pfn(smmu->base) << PAGE_SHIFT);

6. Cancel below union. Whether ECMDQ is enabled is determined only based
on 'ecmdq_enabled'.
-	union {
-		u32			nr_ecmdq;
-		u32			ecmdq_enabled;
-	};
+	u32				nr_ecmdq;
+	bool				ecmdq_enabled;

7. Eliminate some sparse check warnings. For example.
-	struct arm_smmu_ecmdq *ecmdq;
+	struct arm_smmu_ecmdq __percpu *ecmdq;


Zhen Lei (2):
  iommu/arm-smmu-v3: Add support for ECMDQ register mode
  iommu/arm-smmu-v3: Ensure that a set of associated commands are
    inserted in the same ECMDQ

 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 261 +++++++++++++++++++-
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h |  33 +++
 2 files changed, 286 insertions(+), 8 deletions(-)

-- 
2.34.1