Re: [PATCH v4 3/6] iommu/amd: Modify set_dte_entry() to use 256-bit DTE helpers

[Suthikulpanit, Suravee]

On 9/27/2024 2:56 AM, Jason Gunthorpe wrote:
> 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@xxxxxxx>
> > ---
> >   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?

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.

> 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.

We will look to simplify the code in the future.

Thanks,
Suravee