linux-kernel - RE: [PATCH v2 4/4] iommu/vt-d: Remove hard coding PGSNP bit in PASID entries

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Date:   Thu, 5 May 2022 08:46:53 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Lu Baolu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        Jason Gunthorpe <jgg@...dia.com>,
        Alex Williamson <alex.williamson@...hat.com>
CC:     "Pan, Jacob jun" <jacob.jun.pan@...el.com>,
        "Liu, Yi L" <yi.l.liu@...el.com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v2 4/4] iommu/vt-d: Remove hard coding PGSNP bit in PASID
 entries

> From: Lu Baolu <baolu.lu@...ux.intel.com>
> Sent: Thursday, May 5, 2022 9:07 AM
> 
> As enforce_cache_coherency has been introduced into the
> iommu_domain_ops,
> the kernel component which owns the iommu domain is able to opt-in its
> requirement for force snooping support. The iommu driver has no need to
> hard code the page snoop control bit in the PASID table entries anymore.
> 
> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>

Reviewed-by: Kevin Tian <kevin.tian@...el.com>, with one nit:

> ---
>  drivers/iommu/intel/pasid.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/drivers/iommu/intel/pasid.c b/drivers/iommu/intel/pasid.c
> index 41a0e3b02c79..0abfa7fc7fb0 100644
> --- a/drivers/iommu/intel/pasid.c
> +++ b/drivers/iommu/intel/pasid.c
> @@ -710,9 +710,6 @@ int intel_pasid_setup_second_level(struct
> intel_iommu *iommu,
>  	pasid_set_fault_enable(pte);
>  	pasid_set_page_snoop(pte, !!ecap_smpwc(iommu->ecap));

Probably in a separate patch but above should really be renamed
to pasid_set_page_walk_snoop().

> 
> -	if (domain->domain.type == IOMMU_DOMAIN_UNMANAGED)
> -		pasid_set_pgsnp(pte);
> -
>  	/*
>  	 * Since it is a second level only translation setup, we should
>  	 * set SRE bit as well (addresses are expected to be GPAs).
> --
> 2.25.1