linux-kernel - [PATCH v3 0/3] perf/smmuv3: Don't reserve the PMCG register spaces

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Message-ID: <20210127113258.1421-1-thunder.leizhen@huawei.com>
Date:   Wed, 27 Jan 2021 19:32:55 +0800
From:   Zhen Lei <thunder.leizhen@...wei.com>
To:     Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
        "Mark Rutland" <mark.rutland@....com>,
        Joerg Roedel <joro@...tes.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        iommu <iommu@...ts.linux-foundation.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
CC:     Zhen Lei <thunder.leizhen@...wei.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>
Subject: [PATCH v3 0/3] perf/smmuv3: Don't reserve the PMCG register spaces

v2 --> v3:
Patch 3 is updated because https://lkml.org/lkml/2021/1/22/532 has been queued in advance.

v1 --> v2:
According to Robin Murphy's suggestion: https://lkml.org/lkml/2021/1/20/470
Don't reserve the PMCG register spaces, and reserve the entire SMMU register space.

v1:
Since the PMCG may implement its resigters space(4KB Page0 and 4KB Page1)
within the SMMUv3 64KB Page0. In this case, when the SMMUv3 driver reserves the
64KB Page0 resource in advance, the PMCG driver try to reserve its Page0 and
Page1 resources, a resource conflict occurs.

commit 52f3fab0067d6fa ("iommu/arm-smmu-v3: Don't reserve implementation
defined register space") reduce the resource reservation range of the SMMUv3
driver, it only reserves the first 0xe00 bytes in the 64KB Page0, to avoid
the above-mentioned resource conflicts.

But the SMMUv3.3 add support for ECMDQ, its registers space is also implemented
in the SMMUv3 64KB Page0. This means we need to build two separate mappings.
New features may be added in the future, and more independent mappings may be
required. The simple problem is complicated because the user expects to map the
entire SMMUv3 64KB Page0.

Therefore, the proper solution is: If the PMCG register resources are located in
the 64KB Page0 of the SMMU, the PMCG driver does not reserve the conflict resources
when the SMMUv3 driver has reserved the conflict resources before. Instead, the PMCG
driver only performs devm_ioremap() to ensure that it can work properly.

Zhen Lei (3):
  perf/smmuv3: Don't reserve the PMCG register spaces
  perf/smmuv3: Add a MODULE_SOFTDEP() to indicate dependency on SMMU
  iommu/arm-smmu-v3: Reserving the entire SMMU register space

 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 24 ++++--------------------
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h |  2 --
 drivers/perf/arm_smmuv3_pmu.c               | 28 ++++++++++++++++++++++++++--
 3 files changed, 30 insertions(+), 24 deletions(-)

-- 
1.8.3