linux-kernel - Re: [PATCH] fsl_pamu: Use 40-bits for addressing where appropriate

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Message-ID: <20250422190921.GB1213339@ziepe.ca>
Date: Tue, 22 Apr 2025 16:09:21 -0300
From: Jason Gunthorpe <jgg@...pe.ca>
To: iommu@...ts.linux.dev, Joerg Roedel <joro@...tes.org>,
	Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH] fsl_pamu: Use 40-bits for addressing where appropriate

On Mon, Apr 21, 2025 at 10:46:19PM -0400, Ben Collins wrote:
> diff --git a/drivers/iommu/fsl_pamu_domain.c b/drivers/iommu/fsl_pamu_domain.c
> index 30be786bff11e..a4bc6482a00f7 100644
> --- a/drivers/iommu/fsl_pamu_domain.c
> +++ b/drivers/iommu/fsl_pamu_domain.c
> @@ -214,9 +214,10 @@ static struct iommu_domain *fsl_pamu_domain_alloc(unsigned type)
>  	INIT_LIST_HEAD(&dma_domain->devices);
>  	spin_lock_init(&dma_domain->domain_lock);
>  
> -	/* default geometry 64 GB i.e. maximum system address */
> +	/* Set default geometry based on physical address limit. */
>  	dma_domain->iommu_domain. geometry.aperture_start = 0;
> -	dma_domain->iommu_domain.geometry.aperture_end = (1ULL << 36) - 1;
> +	dma_domain->iommu_domain.geometry.aperture_end =
> +		(1ULL << PAMU_MAX_PHYS_BITS) - 1;
>  	dma_domain->iommu_domain.geometry.force_aperture = true;

What on earth does this even do? There is no map_range() callback in
this driver, so nothing should be reading geometry..

Jason