Re: [PATCH 06/11] iommu/amd: Refactor helper function for attaching / detaching device

[Jason Gunthorpe <jgg@ziepe.ca>]

On Tue, Aug 08, 2023 at 10:02:27AM +0000, Vasant Hegde wrote:
> From: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
> 
> To use the new helper function for setting up GCR3 table.
> 
> If system is booted with V2 page table then setup default GCR3 with
> domain GCR3 pointer. So that all devices in the domain uses same page
> table for translation. Also return page table setup status from
> do_attach() function.
> 
> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
> Co-developed-by: Vasant Hegde <vasant.hegde@amd.com>
> Signed-off-by: Vasant Hegde <vasant.hegde@amd.com>
> ---
>  drivers/iommu/amd/iommu.c | 54 ++++++++++++++++++++++++++++++++++++---
>  1 file changed, 50 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
> index cc42732820dd..4fed3fbe069e 100644
> --- a/drivers/iommu/amd/iommu.c
> +++ b/drivers/iommu/amd/iommu.c
> @@ -1821,15 +1821,41 @@ static void clear_dte_entry(struct amd_iommu *iommu, u16 devid)
>  	amd_iommu_apply_erratum_63(iommu, devid);
>  }
>  
> -static void do_attach(struct iommu_dev_data *dev_data,
> -		      struct protection_domain *domain)
> +/*
> + * Note: This is currently used when booting w/ amd_iommu=pgtbl_v2
> + */

I would drop all this commentary about amd_iommu=pgtbl_v2. That
command line option should be removed.

This is more about enabling the GCR3 when PASID is required.

> +static int default_gcr3_init(struct iommu_dev_data *dev_data)
> +{

I wouldn't call it default. On the ARM series we've been calling this
the 'kernel owned PASID table'. It simply IS the GCR3 table for this
struct device.

Jason