linux-kernel - Re: [RFC PATCH 7/7] iommu/amd: Add support for using AMD IOMMU v2 page table for DMA-API

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Date:   Thu, 18 Mar 2021 16:44:49 +0100
From:   Joerg Roedel <joro@...tes.org>
To:     Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Cc:     linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org,
        Jon.Grimm@....com, Wei.Huang2@....com
Subject: Re: [RFC PATCH 7/7] iommu/amd: Add support for using AMD IOMMU v2
 page table for DMA-API

On Fri, Mar 12, 2021 at 03:04:11AM -0600, Suravee Suthikulpanit wrote:
> Introduce init function for setting up DMA domain for DMA-API with
> the IOMMU v2 page table.
> 
> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
> ---
>  drivers/iommu/amd/iommu.c | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
> 
> diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
> index e29ece6e1e68..bd26de8764bd 100644
> --- a/drivers/iommu/amd/iommu.c
> +++ b/drivers/iommu/amd/iommu.c
> @@ -1937,6 +1937,24 @@ static int protection_domain_init_v1(struct protection_domain *domain, int mode)
>  	return 0;
>  }
>  
> +static int protection_domain_init_v2(struct protection_domain *domain)
> +{
> +	spin_lock_init(&domain->lock);
> +	domain->id = domain_id_alloc();
> +	if (!domain->id)
> +		return -ENOMEM;
> +	INIT_LIST_HEAD(&domain->dev_list);
> +
> +	domain->giov = true;
> +
> +	if (amd_iommu_pgtable == AMD_IOMMU_V2 &&
> +	    domain_enable_v2(domain, 1, false)) {
> +		return -ENOMEM;
> +	}
> +
> +	return 0;
> +}
> +

You also need to advertise a different aperture size and a different
pgsize-bitmap. The host page-table can only map a 48 bit address space,
not a 64 bit one like with v1 page-tables.

Regards,

	Joerg