[PATCH] iommu/sun50i: Remove IOMMU_DOMAIN_IDENTITY

[PATCH] iommu/sun50i: Remove IOMMU_DOMAIN_IDENTITY

[Jason Gunthorpe]

This driver treats IOMMU_DOMAIN_IDENTITY the same as UNMANAGED, which
cannot possibly be correct.

UNMANAGED domains are required to start out blocking all DMAs. This seems
to be what this driver does as it allocates a first level 'dt' for the IO
page table that is 0 filled.

Thus UNMANAGED looks like a working IO page table, and so IDENTITY must be
a mistake. Remove it.

Fixes: 4100b8c229b3 ("iommu: Add Allwinner H6 IOMMU driver")
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
 drivers/iommu/sun50i-iommu.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/iommu/sun50i-iommu.c b/drivers/iommu/sun50i-iommu.c
index cd9b74ee24def1..0843418434ff3a 100644
--- a/drivers/iommu/sun50i-iommu.c
+++ b/drivers/iommu/sun50i-iommu.c
@@ -601,7 +601,6 @@ static struct iommu_domain *sun50i_iommu_domain_alloc(unsigned type)
 	struct sun50i_iommu_domain *sun50i_domain;
 
 	if (type != IOMMU_DOMAIN_DMA &&
-	    type != IOMMU_DOMAIN_IDENTITY &&
 	    type != IOMMU_DOMAIN_UNMANAGED)
 		return NULL;
 

base-commit: 328827239b9ce3a95b5c0d33e8875651580de053
-- 
2.38.1


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Re: [PATCH] iommu/sun50i: Remove IOMMU_DOMAIN_IDENTITY

[Robin Murphy]

On 2022-11-28 14:06, Jason Gunthorpe wrote:
> This driver treats IOMMU_DOMAIN_IDENTITY the same as UNMANAGED, which
> cannot possibly be correct.
> 
> UNMANAGED domains are required to start out blocking all DMAs. This seems
> to be what this driver does as it allocates a first level 'dt' for the IO
> page table that is 0 filled.
> 
> Thus UNMANAGED looks like a working IO page table, and so IDENTITY must be
> a mistake. Remove it.

Ah yes, this did once catch my eye ages ago and Andre confirmed that 
real hardware fell over with "iommu.passthrough=1", but it seems we both 
forgot about it again before a patch got written. Thanks for taking the 
time!

Reviewed-by: Robin Murphy <robin.murphy@arm.com>

> Fixes: 4100b8c229b3 ("iommu: Add Allwinner H6 IOMMU driver")
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> ---
>   drivers/iommu/sun50i-iommu.c | 1 -
>   1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/iommu/sun50i-iommu.c b/drivers/iommu/sun50i-iommu.c
> index cd9b74ee24def1..0843418434ff3a 100644
> --- a/drivers/iommu/sun50i-iommu.c
> +++ b/drivers/iommu/sun50i-iommu.c
> @@ -601,7 +601,6 @@ static struct iommu_domain *sun50i_iommu_domain_alloc(unsigned type)
>   	struct sun50i_iommu_domain *sun50i_domain;
>   
>   	if (type != IOMMU_DOMAIN_DMA &&
> -	    type != IOMMU_DOMAIN_IDENTITY &&
>   	    type != IOMMU_DOMAIN_UNMANAGED)
>   		return NULL;
>   
> 
> base-commit: 328827239b9ce3a95b5c0d33e8875651580de053

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Re: [PATCH] iommu/sun50i: Remove IOMMU_DOMAIN_IDENTITY

[Joerg Roedel]

On Mon, Nov 28, 2022 at 10:06:28AM -0400, Jason Gunthorpe wrote:
> This driver treats IOMMU_DOMAIN_IDENTITY the same as UNMANAGED, which
> cannot possibly be correct.
> 
> UNMANAGED domains are required to start out blocking all DMAs. This seems
> to be what this driver does as it allocates a first level 'dt' for the IO
> page table that is 0 filled.
> 
> Thus UNMANAGED looks like a working IO page table, and so IDENTITY must be
> a mistake. Remove it.
> 
> Fixes: 4100b8c229b3 ("iommu: Add Allwinner H6 IOMMU driver")
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

Applied, thanks.


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