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Date:   Mon, 7 Nov 2022 15:26:45 +0000
From:   Will Deacon <will@kernel.org>
To:     Nicolin Chen <nicolinc@nvidia.com>
Cc:     joro@8bytes.org, robin.murphy@arm.com, jgg@nvidia.com,
        kevin.tian@intel.com, quic_jjohnson@quicinc.com,
        suravee.suthikulpanit@amd.com, robdclark@gmail.com,
        dwmw2@infradead.org, baolu.lu@linux.intel.com,
        yong.wu@mediatek.com, matthias.bgg@gmail.com, orsonzhai@gmail.com,
        baolin.wang@linux.alibaba.com, zhang.lyra@gmail.com,
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        jean-philippe@linaro.org, tglx@linutronix.de,
        shameerali.kolothum.thodi@huawei.com,
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        yangyingliang@huawei.com, quic_saipraka@quicinc.com,
        jon@solid-run.com, iommu@lists.linux.dev,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
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        virtualization@lists.linux-foundation.org
Subject: Re: [PATCH v7 4/5] iommu: Use EINVAL for incompatible device/domain
 in ->attach_dev
Message-ID: <20221107152645.GD21002@willie-the-truck>
References: <cover.1666042872.git.nicolinc@nvidia.com>
 <f52a07f7320da94afe575c9631340d0019a203a7.1666042873.git.nicolinc@nvidia.com>
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On Mon, Oct 17, 2022 at 04:02:21PM -0700, Nicolin Chen wrote:
> Following the new rules in include/linux/iommu.h kdocs, update all drivers
> ->attach_dev callback functions to return EINVAL in the failure paths that
> are related to domain incompatibility.
> 
> Also, drop adjacent error prints to prevent a kernel log spam.
> 
> Reviewed-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
> Reviewed-by: Kevin Tian <kevin.tian@intel.com>
> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
> Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
> ---
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 11 +----------
>  drivers/iommu/arm/arm-smmu/arm-smmu.c       |  3 ---
>  drivers/iommu/arm/arm-smmu/qcom_iommu.c     |  7 +------
>  drivers/iommu/intel/iommu.c                 | 10 +++-------
>  drivers/iommu/ipmmu-vmsa.c                  |  2 --
>  drivers/iommu/omap-iommu.c                  |  2 +-
>  drivers/iommu/sprd-iommu.c                  |  4 +---
>  drivers/iommu/tegra-gart.c                  |  2 +-
>  drivers/iommu/virtio-iommu.c                |  3 +--
>  9 files changed, 9 insertions(+), 35 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 ba47c73f5b8c..01fd7df16cb9 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> @@ -2430,23 +2430,14 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
>  			goto out_unlock;
>  		}
>  	} else if (smmu_domain->smmu != smmu) {
> -		dev_err(dev,
> -			"cannot attach to SMMU %s (upstream of %s)\n",
> -			dev_name(smmu_domain->smmu->dev),
> -			dev_name(smmu->dev));
> -		ret = -ENXIO;
> +		ret = -EINVAL;
>  		goto out_unlock;
>  	} else if (smmu_domain->stage == ARM_SMMU_DOMAIN_S1 &&
>  		   master->ssid_bits != smmu_domain->s1_cfg.s1cdmax) {
> -		dev_err(dev,
> -			"cannot attach to incompatible domain (%u SSID bits != %u)\n",
> -			smmu_domain->s1_cfg.s1cdmax, master->ssid_bits);
>  		ret = -EINVAL;
>  		goto out_unlock;
>  	} else if (smmu_domain->stage == ARM_SMMU_DOMAIN_S1 &&
>  		   smmu_domain->stall_enabled != master->stall_enabled) {
> -		dev_err(dev, "cannot attach to stall-%s domain\n",
> -			smmu_domain->stall_enabled ? "enabled" : "disabled");
>  		ret = -EINVAL;
>  		goto out_unlock;
>  	}

I think it would be helpful to preserve these messages using
dev_err_ratelimited() so that attach failure can be diagnosed without
having to hack the messages back into the driver.

With that:

Acked-by: Will Deacon <will@kernel.org>

Will