linux-kernel - RE: [PATCH v4 05/12] iommu/vt-d: Reserve a domain id for FL and PT modes

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Message-ID: <A2975661238FB949B60364EF0F2C257439D5FAE7@SHSMSX104.ccr.corp.intel.com>
Date:   Wed, 7 Nov 2018 06:55:38 +0000
From:   "Liu, Yi L" <yi.l.liu@...el.com>
To:     Lu Baolu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>
CC:     "Raj, Ashok" <ashok.raj@...el.com>,
        "Kumar, Sanjay K" <sanjay.k.kumar@...el.com>,
        "Pan, Jacob jun" <jacob.jun.pan@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        "Sun, Yi Y" <yi.y.sun@...el.com>,
        "peterx@...hat.com" <peterx@...hat.com>,
        Jean-Philippe Brucker <jean-philippe.brucker@....com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>
Subject: RE: [PATCH v4 05/12] iommu/vt-d: Reserve a domain id for FL and PT
 modes

Hi Baolu,

> From: Lu Baolu [mailto:baolu.lu@...ux.intel.com]
> Sent: Monday, November 5, 2018 1:32 PM
> Subject: [PATCH v4 05/12] iommu/vt-d: Reserve a domain id for FL and PT modes
> 
> Vt-d spec rev3.0 (section 6.2.3.1) requires that each pasid
> entry for first-level or pass-through translation should be
> programmed with a domain id different from those used for
> second-level or nested translation. It is recommended that
> software could use a same domain id for all first-only and
> pass-through translations.
> 
> This reserves a domain id for first-level and pass-through
> translations.
> 
> Cc: Ashok Raj <ashok.raj@...el.com>
> Cc: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> Cc: Kevin Tian <kevin.tian@...el.com>
> Cc: Liu Yi L <yi.l.liu@...el.com>
> Cc: Sanjay Kumar <sanjay.k.kumar@...el.com>
> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
> ---
>  drivers/iommu/intel-iommu.c | 10 ++++++++++
>  drivers/iommu/intel-pasid.h |  6 ++++++
>  2 files changed, 16 insertions(+)
> 
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index 9331240c70b8..2f7455ee4e7a 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -1618,6 +1618,16 @@ static int iommu_init_domains(struct intel_iommu
> *iommu)
>  	 */
>  	set_bit(0, iommu->domain_ids);
> 
> +	/*
> +	 * Vt-d spec rev3.0 (section 6.2.3.1) requires that each pasid
> +	 * entry for first-level or pass-through translation modes should
> +	 * be programmed with a domain id different from those used for
> +	 * second-level or nested translation. We reserve a domain id for
> +	 * this purpose.
> +	 */
> +	if (sm_supported(iommu))
> +		set_bit(FLPT_DEFAULT_DID, iommu->domain_ids);

"FLPT_DEFAULT_DID" looks very likely for first level translation. How about
"PT_FL_DEFAULT_DID"?

>  	return 0;
>  }
> 
> diff --git a/drivers/iommu/intel-pasid.h b/drivers/iommu/intel-pasid.h
> index 12f480c2bb8b..03c1612d173c 100644
> --- a/drivers/iommu/intel-pasid.h
> +++ b/drivers/iommu/intel-pasid.h
> @@ -17,6 +17,12 @@
>  #define PDE_PFN_MASK			PAGE_MASK
>  #define PASID_PDE_SHIFT			6
> 
> +/*
> + * Domain ID reserved for pasid entries programmed for first-level
> + * only and pass-through transfer modes.
> + */
> +#define FLPT_DEFAULT_DID		1

Would be helpful to elaborate why DID 1 is selected in the patch
description.

Regards,
Yi Liu