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SubjectRe: [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@amd.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

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