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Subject: Re: [PATCH v2 24/24] iommu: Only log strictness for DMA domains
To:     Robin Murphy <robin.murphy@arm.com>, <joro@8bytes.org>,
        <will@kernel.org>
CC:     <iommu@lists.linux-foundation.org>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-kernel@vger.kernel.org>, <suravee.suthikulpanit@amd.com>,
        <baolu.lu@linux.intel.com>, <dianders@chromium.org>
References: <cover.1627468308.git.robin.murphy@arm.com>
 <b2da9ba999b54acded9198cf92cf9b7d0fce1b45.1627468310.git.robin.murphy@arm.com>
From:   John Garry <john.garry@huawei.com>
Message-ID: <d679940d-6781-c850-7eb1-07b7b0864d2a@huawei.com>
Date:   Thu, 29 Jul 2021 10:04:31 +0100
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On 28/07/2021 16:58, Robin Murphy wrote:
> When passthrough is enabled, the default strictness policy becomes
> irrelevant, since any subsequent runtime override to a DMA domain type
> now embodies an explicit choice of strictness as well. Save on noise by
> only logging the default policy when it is meaningfully in effect.
> 
> Signed-off-by: Robin Murphy<robin.murphy@arm.com>

FWIW, small comment below,

Reviewed-by: John Garry <john.garry@huawei.com>

> ---
>   drivers/iommu/iommu.c | 9 +++++----
>   1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index be399d630953..87d7b299436e 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -144,10 +144,11 @@ static int __init iommu_subsys_init(void)
>   		(iommu_cmd_line & IOMMU_CMD_LINE_DMA_API) ?
>   			"(set via kernel command line)" : "");
>   
> -	pr_info("DMA domain TLB invalidation policy: %s mode %s\n",
> -		iommu_dma_strict ? "strict" : "lazy",
> -		(iommu_cmd_line & IOMMU_CMD_LINE_STRICT) ?
> -			"(set via kernel command line)" : "");
> +	if (!iommu_default_passthrough())

I suppose that you could also do an early return to save indenting...


> +		pr_info("DMA domain TLB invalidation policy: %s mode %s\n",
> +			iommu_dma_strict ? "strict" : "lazy",
> +			(iommu_cmd_line & IOMMU_CMD_LINE_STRICT) ?
> +				"(set via kernel command line)" : "");
>   
>   	return 0;
>   }