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Subject: Re: [PATCH v11 03/10] iommu/vt-d: Use a helper function to skip agaw
 for SL
To:     Jacob Pan <jacob.jun.pan@linux.intel.com>,
        Lu Baolu <baolu.lu@linux.intel.com>,
        iommu@lists.linux-foundation.org,
        LKML <linux-kernel@vger.kernel.org>,
        Joerg Roedel <joro@8bytes.org>,
        David Woodhouse <dwmw2@infradead.org>,
        Jean-Philippe Brucker <jean-philippe@linaro.com>
Cc:     Yi Liu <yi.l.liu@intel.com>, "Tian, Kevin" <kevin.tian@intel.com>,
        Raj Ashok <ashok.raj@intel.com>,
        Alex Williamson <alex.williamson@redhat.com>,
        Christoph Hellwig <hch@infradead.org>,
        Jonathan Cameron <jic23@kernel.org>
References: <1585939334-21396-1-git-send-email-jacob.jun.pan@linux.intel.com>
 <1585939334-21396-4-git-send-email-jacob.jun.pan@linux.intel.com>
From:   Auger Eric <eric.auger@redhat.com>
Message-ID: <54625f36-909e-405d-fe8d-e80f4314646a@redhat.com>
Date:   Sun, 5 Apr 2020 08:37:23 +0200
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Hi Jacob,

On 4/3/20 8:42 PM, Jacob Pan wrote:
> An Intel iommu domain uses 5-level page table by default. If the
> iommu that the domain tries to attach supports less page levels,
> the top level page tables should be skipped. Add a helper to do
> this so that it could be used in other places.
> 
> ---
> v11 Added Baolu's commit message and squashed 4 & 5 from v10.
> ---
> 
> Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>

Eric
> ---
>  drivers/iommu/intel-pasid.c | 34 ++++++++++++++++++++++++----------
>  1 file changed, 24 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/iommu/intel-pasid.c b/drivers/iommu/intel-pasid.c
> index 22b30f10b396..66c364719ad1 100644
> --- a/drivers/iommu/intel-pasid.c
> +++ b/drivers/iommu/intel-pasid.c
> @@ -500,6 +500,26 @@ int intel_pasid_setup_first_level(struct intel_iommu *iommu,
>  }
>  
>  /*
> + * Skip top levels of page tables for iommu which has less agaw
> + * than default. Unnecessary for PT mode.
> + */
> +static inline int iommu_skip_agaw(struct dmar_domain *domain,
> +				  struct intel_iommu *iommu,
> +				  struct dma_pte **pgd)
> +{
> +	int agaw;
> +
> +	for (agaw = domain->agaw; agaw > iommu->agaw; agaw--) {
> +		*pgd = phys_to_virt(dma_pte_addr(*pgd));
> +		if (!dma_pte_present(*pgd)) {
> +			return -EINVAL;
> +		}
> +	}
> +
> +	return agaw;
> +}
> +
> +/*
>   * Set up the scalable mode pasid entry for second only translation type.
>   */
>  int intel_pasid_setup_second_level(struct intel_iommu *iommu,
> @@ -522,17 +542,11 @@ int intel_pasid_setup_second_level(struct intel_iommu *iommu,
>  		return -EINVAL;
>  	}
>  
> -	/*
> -	 * Skip top levels of page tables for iommu which has less agaw
> -	 * than default. Unnecessary for PT mode.
> -	 */
>  	pgd = domain->pgd;
> -	for (agaw = domain->agaw; agaw > iommu->agaw; agaw--) {
> -		pgd = phys_to_virt(dma_pte_addr(pgd));
> -		if (!dma_pte_present(pgd)) {
> -			dev_err(dev, "Invalid domain page table\n");
> -			return -EINVAL;
> -		}
> +	agaw = iommu_skip_agaw(domain, iommu, &pgd);
> +	if (agaw < 0) {
> +		dev_err(dev, "Invalid domain page table\n");
> +		return -EINVAL;
>  	}
>  
>  	pgd_val = virt_to_phys(pgd);
>