From: Thierry Reding <thierry.reding@gmail.com>
To: Nicolin Chen <nicoleotsuka@gmail.com>
Cc: joro@8bytes.org, vdumpa@nvidia.com, jonathanh@nvidia.com,
digetx@gmail.com, linux-tegra@vger.kernel.org,
iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
hch@infradead.org
Subject: Re: [PATCH v4 1/2] iommu/tegra-smmu: Unwrap tegra_smmu_group_get
Date: Thu, 8 Oct 2020 11:55:50 +0200 [thread overview]
Message-ID: <20201008095550.GB2349275@ulmo> (raw)
In-Reply-To: <20200929061325.10197-2-nicoleotsuka@gmail.com>
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On Mon, Sep 28, 2020 at 11:13:24PM -0700, Nicolin Chen wrote:
> The tegra_smmu_group_get was added to group devices in different
> SWGROUPs and it'd return a NULL group pointer upon a mismatch at
> tegra_smmu_find_group(), so for most of clients/devices, it very
> likely would mismatch and need a fallback generic_device_group().
>
> But now tegra_smmu_group_get handles devices in same SWGROUP too,
> which means that it would allocate a group for every new SWGROUP
> or would directly return an existing one upon matching a SWGROUP,
> i.e. any device will go through this function.
>
> So possibility of having a NULL group pointer in device_group()
> is upon failure of either devm_kzalloc() or iommu_group_alloc().
> In either case, calling generic_device_group() no longer makes a
> sense. Especially for devm_kzalloc() failing case, it'd cause a
> problem if it fails at devm_kzalloc() yet succeeds at a fallback
> generic_device_group(), because it does not create a group->list
> for other devices to match.
>
> This patch simply unwraps the function to clean it up.
>
> Signed-off-by: Nicolin Chen <nicoleotsuka@gmail.com>
> ---
>
> Changelog
> v2->v4:
> * N/A
> v1->v2:
> * Changed type of swgroup to "unsigned int", following Thierry's
> commnets.
>
> drivers/iommu/tegra-smmu.c | 19 ++++---------------
> 1 file changed, 4 insertions(+), 15 deletions(-)
Acked-by: Thierry Reding <treding@nvidia.com>
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next prev parent reply other threads:[~2020-10-08 9:55 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-29 6:13 [PATCH v4 0/2] iommu/tegra-smmu: Two followup changes Nicolin Chen
2020-09-29 6:13 ` [PATCH v4 1/2] iommu/tegra-smmu: Unwrap tegra_smmu_group_get Nicolin Chen
2020-09-29 17:41 ` Dmitry Osipenko
2020-10-03 14:27 ` Dmitry Osipenko
2020-10-08 9:55 ` Thierry Reding [this message]
2020-09-29 6:13 ` [PATCH v4 2/2] iommu/tegra-smmu: Expand mutex protection range Nicolin Chen
2020-09-29 17:42 ` Dmitry Osipenko
2020-09-30 0:31 ` Nicolin Chen
2020-10-03 14:28 ` Dmitry Osipenko
2020-10-08 9:56 ` Thierry Reding
2020-11-07 8:35 ` [PATCH v4 0/2] iommu/tegra-smmu: Two followup changes Nicolin Chen
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