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

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Message-ID: <20241003184931.GC1365916@nvidia.com>
Date: Thu, 3 Oct 2024 15:49:31 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: "Suthikulpanit, Suravee" <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 Thu, Oct 03, 2024 at 11:16:19PM +0700, Suthikulpanit, Suravee wrote:

> > > +	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?
> 
> The GCR3 table is also used when we setup v2 table for SVA stuff. In such
> case, we would be setting up w/ PASID. Therefore, the GIOV bit is not
> needed.

If I understand the manual right this should be written as:

if (dev_data->domain->type != IDENTITY)
   target->data[0] |= DTE_FLAG_GIOV;

Ie everything on the RID except identity should be translated through
PASID 0 and if PASID 0 is a V2 page table then it will translate and
if PASID 0 is non-valid then it will block?

Identity needs to not use GIOV otherwise it will be blocking?

Jason