linux-kernel - Re: [PATCH] iommu/dma: Fix domain init

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Message-ID: <jrzrf3vz2rhcrwazsxuljuyhru4mstyzuhjx4uawcfmjlmvipd@lu6usxz22ved>
Date: Mon, 20 May 2024 21:45:43 -0700
From: Jerry Snitselaar <jsnitsel@...hat.com>
To: Robin Murphy <robin.murphy@....com>
Cc: joro@...tes.org, iommu@...ts.linux.dev, will@...nel.org, 
	linux-kernel@...r.kernel.org, Jon Hunter <jonathanh@...dia.com>
Subject: Re: [PATCH] iommu/dma: Fix domain init

On Mon, May 20, 2024 at 08:14:44PM GMT, Robin Murphy wrote:
> Despite carefully rewording the kerneldoc to describe the new direct
> interaction with dma_range_map, it seems I managed to confuse myself in
> removing the redundant force_aperture check and ended up making the code
> not do that at all. This led to dma_range_maps inadvertently being able
> to set iovad->start_pfn = 0, and all the nonsensical chaos which ensues
> from there. Restore the correct behaviour of constraining base_pfn to
> the domain aperture regardless of dma_range_map, and not trying to apply
> dma_range_map constraints to the basic IOVA domain since they will be
> properly handled with reserved regions later.
> 
> Reported-by: Jon Hunter <jonathanh@...dia.com>
> Reported-by: Jerry Snitselaar <jsnitsel@...hat.com>
> Fixes: e28a114243d1 ("iommu/dma: Make limit checks self-contained")

I'm seeing this upstream as ad4750b07d34 ("iommu/dma: Make limit checks self-contained") now.

> Signed-off-by: Robin Murphy <robin.murphy@....com>
> ---

Tested-by: Jerry Snitselaar <jsnitsel@...hat.com>
Reviewed-by: Jerry Snitselaar <jsnitsel@...hat.com>

>  drivers/iommu/dma-iommu.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index 89a53c2f2cf9..1ec89ca75c59 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -685,15 +685,15 @@ static int iommu_dma_init_domain(struct iommu_domain *domain, struct device *dev
>  
>  	/* Check the domain allows at least some access to the device... */
>  	if (map) {
> -		dma_addr_t base = dma_range_map_min(map);
> -		if (base > domain->geometry.aperture_end ||
> +		if (dma_range_map_min(map) > domain->geometry.aperture_end ||
>  		    dma_range_map_max(map) < domain->geometry.aperture_start) {
>  			pr_warn("specified DMA range outside IOMMU capability\n");
>  			return -EFAULT;
>  		}
> -		/* ...then finally give it a kicking to make sure it fits */
> -		base_pfn = max(base, domain->geometry.aperture_start) >> order;
>  	}
> +	/* ...then finally give it a kicking to make sure it fits */
> +	base_pfn = max_t(unsigned long, base_pfn,
> +			 domain->geometry.aperture_start >> order);
>  
>  	/* start_pfn is always nonzero for an already-initialised domain */
>  	mutex_lock(&cookie->mutex);
> -- 
> 2.39.2.101.g768bb238c484.dirty
>