linux-kernel - Re: [PATCH v4 3/6] iommu/amd: Modify set_dte

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Message-ID: <20240926195648.GA229871@nvidia.com>
Date: Thu, 26 Sep 2024 16:56:48 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Cc: linux-kernel@...r.kernel.org, iommu@...ts.linux.dev, joro@...tes.org,
	robin.murphy@....com, vasant.hegde@....com, kevin.tian@...el.com,
	jon.grimm@....com, santosh.shukla@....com, pandoh@...gle.com,
	kumaranand@...gle.com
Subject: Re: [PATCH v4 3/6] iommu/amd: Modify set_dte_entry() to use 256-bit
 DTE helpers

On Mon, Sep 16, 2024 at 05:18:02PM +0000, Suravee Suthikulpanit wrote:
> Also, the set_dte_entry() is used to program several DTE fields (e.g.
> stage1 table, stage2 table, domain id, and etc.), which is difficult
> to keep track with current implementation.
> 
> Therefore, separate logic for setting up the GCR3 Table Root Pointer,
> GIOV, GV, GLX, and GuestPagingMode into another helper function
> set_dte_gcr3_table().
> 
> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
> ---
>  drivers/iommu/amd/iommu.c | 117 +++++++++++++++++++++-----------------
>  1 file changed, 65 insertions(+), 52 deletions(-)
> 
> diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
> index 48a721d10f06..12f27061680d 100644
> --- a/drivers/iommu/amd/iommu.c
> +++ b/drivers/iommu/amd/iommu.c
> @@ -1947,17 +1947,58 @@ int amd_iommu_clear_gcr3(struct iommu_dev_data *dev_data, ioasid_t pasid)
>  	return ret;
>  }
>  
> +static void set_dte_gcr3_table(struct amd_iommu *iommu,
> +			       struct iommu_dev_data *dev_data,
> +			       struct dev_table_entry *target)
> +{
> +	struct gcr3_tbl_info *gcr3_info = &dev_data->gcr3_info;
> +	u64 tmp, gcr3;
> +
> +	if (!gcr3_info->gcr3_tbl)
> +		return;
> +
> +	pr_debug("%s: devid=%#x, glx=%#x, gcr3_tbl=%#llx\n",
> +		 __func__, dev_data->devid, gcr3_info->glx,
> +		 (unsigned long long)gcr3_info->gcr3_tbl);
> +
> +	tmp = gcr3_info->glx;
> +	target->data[0] |= (tmp & DTE_GLX_MASK) << DTE_GLX_SHIFT;
> +	if (pdom_is_v2_pgtbl_mode(dev_data->domain))
> +		target->data[0] |= DTE_FLAG_GIOV;

When does this get called to install a gcr3 table without a v2 domain?

Other than my remark on patch 5 this looks Ok to me and making a
helper function for the gcr3 case is a good step forward.

Suggest you follow up with helper functions for blocking, identity and
v1 as well :) Then it will be really easy to follow.

Thanks,
Jason