linux-kernel - Re: [PATCH] iommu: Print default strict or lazy mode at init time

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Message-ID: <3ee986a0-29c1-100c-c72f-360f919caf7d@arm.com>
Date:   Tue, 1 Jun 2021 10:09:50 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     John Garry <john.garry@...wei.com>, joro@...tes.org,
        will@...nel.org
Cc:     iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        hch@....de
Subject: Re: [PATCH] iommu: Print default strict or lazy mode at init time

On 2021-05-28 14:37, John Garry wrote:
> As well as the default domain type, it's useful to know whether strict
> or lazy mode is default for DMA domains, so add this info in a separate
> print.
> 
> Signed-off-by: John Garry <john.garry@...wei.com>
> 
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 808ab70d5df5..f25fae62f077 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -138,6 +138,11 @@ static int __init iommu_subsys_init(void)
>   		(iommu_cmd_line & IOMMU_CMD_LINE_DMA_API) ?
>   			"(set via kernel command line)" : "");
>   
> +	pr_info("Default DMA domain mode: %s %s\n",

Nit: I think this might be a little unclear for end-users - *I'm* not 
even sure whether "Default" here is meant to refer to the mode setting 
itself or to default domains (of DMA type). Maybe something like "DMA 
domain TLB invalidation policy"? Certainly it seems like a good idea to 
explicitly mention invalidation to correlate with the documentation of 
the "iommu.strict" parameter.

Ack to the general idea though.

Thanks,
Robin.

> +		iommu_dma_strict ? "strict" : "lazy",
> +		(iommu_cmd_line & IOMMU_CMD_LINE_STRICT) ?
> +			"(set via kernel command line)" : "");
> +
>   	return 0;
>   }
>   subsys_initcall(iommu_subsys_init);
>