linux-kernel - Re: [PATCH] iommu/dma: Reserve iova ranges for reserved regions of all devices

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Message-ID: <vup5ms2p5o4ao3t57kfgqtnnna7e4jcvkvup2vmyf6o4qrb3qu@3aanawjzggyh>
Date: Wed, 6 Nov 2024 12:13:45 -0700
From: Jerry Snitselaar <jsnitsel@...hat.com>
To: iommu@...ts.linux.dev
Cc: Robin Murphy <robin.murphy@....com>, Joerg Roedel <joro@...tes.org>, 
	Will Deacon <will@...nel.org>, linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] iommu/dma: Reserve iova ranges for reserved regions of
 all devices

On Thu, Oct 24, 2024 at 08:34:12AM -0700, Jerry Snitselaar wrote:
> Only the first device that is passed when the domain is set up will
> have its reserved regions reserved in the iova address space.  So if
> there are other devices in the group with unique reserved regions,
> those regions will not get reserved in the iova address space.  All of
> the ranges do get set up in the iopagetables via calls to
> iommu_create_device_direct_mappings for all devices in a group.
> 
> In the case of vt-d system this resulted in messages like the following:
> 
> [ 1632.693264] DMAR: ERROR: DMA PTE for vPFN 0xf1f7e already set (to f1f7e003 not 173025001)
> 
> To make sure iova ranges are reserved for the reserved regions all of
> the devices, call iova_reserve_iommu_regions in iommu_dma_init_domain
> prior to exiting in the case where the domain is already initialized.
> 
> Cc: Robin Murphy <robin.murphy@....com>
> Cc: Joerg Roedel <joro@...tes.org>
> Cc: Will Deacon <will@...nel.org>
> Cc: linux-kernel@...r.kernel.org
> Cc: stable@...r.kernel.org
> Fixes: 7c1b058c8b5a ("iommu/dma: Handle IOMMU API reserved regions")
> Signed-off-by: Jerry Snitselaar <jsnitsel@...hat.com>
> ---
> Robin: I wasn't positive if this is the correct solution, or if it should be
>        done for the entire group at once.
> 
>  drivers/iommu/dma-iommu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index 2a9fa0c8cc00..5fd3cccbb233 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -707,7 +707,7 @@ static int iommu_dma_init_domain(struct iommu_domain *domain, struct device *dev
>  			goto done_unlock;
>  		}
>  
> -		ret = 0;
> +		ret = iova_reserve_iommu_regions(dev, domain);
>  		goto done_unlock;
>  	}
>  
> -- 
> 2.44.0
> 

Robin,

Any thoughts on this patch? In the case where this originally popped
up it was likely a crap DMAR table in an HPE system with an ilo, as
the RMRR in question had a device in the list that as far as I could
tell didn't actually exist. The 2nd function of the sata controller
was in the list, but not the first, and the first function was the
device where the group/domain was initialized. With some debugging
code I could see it set up the ioptes for the 2nd function, but it
wasn't reserving the range of iovas.


Regards,
Jerry