linux-kernel - Re: [PATCH v2] iommu/intel-iommu: fix pasid table size encoding

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Message-ID: <87lgvi8z6v.fsf@gaia.fi.intel.com>
Date:   Wed, 14 Dec 2016 14:36:40 +0200
From:   Mika Kuoppala <mika.kuoppala@...ux.intel.com>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Joerg Roedel <joro@...tes.org>,
        LKML <linux-kernel@...r.kernel.org>,
        iommu@...ts.linux-foundation.org
Cc:     Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Ashok Raj <ashok.raj@...el.com>
Subject: Re: [PATCH v2] iommu/intel-iommu: fix pasid table size encoding

Jacob Pan <jacob.jun.pan@...ux.intel.com> writes:

> Different encodings are used to represent supported PASID bits
> and number of PASID table entries.
> The current code assigns ecap_pss directly to extended context
> table entry PTS which is wrong and could result in writing
> non-zero bits to the reserved fields. IOMMU fault reason
> 11 will be reported when reserved bits are nonzero.
> This patch converts ecap_pss to extend context entry pts encoding
> based on VT-d spec. Chapter 9.4 as follows:
>  - number of PASID bits = ecap_pss + 1
>  - number of PASID table entries = 2^(pts + 5)
> Software assigned limit of pasid_max value is also respected to
> match the allocation limitation of PASID table.
>
> cc: Mika Kuoppala <mika.kuoppala@...ux.intel.com>
> cc: Ashok Raj <ashok.raj@...el.com>
> Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>

Tested-by: Mika Kuoppala <mika.kuoppala@...el.com>

> ---
>  drivers/iommu/intel-iommu.c | 23 ++++++++++++++++++++++-
>  1 file changed, 22 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index 27596e6..5d9cddc 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -5173,6 +5173,25 @@ static void intel_iommu_remove_device(struct device *dev)
>  }
>  
>  #ifdef CONFIG_INTEL_IOMMU_SVM
> +#define MAX_NR_PASID_BITS (20)
> +static inline unsigned long intel_iommu_get_pts(struct intel_iommu *iommu)
> +{
> +	/*
> +	 * Convert ecap_pss to extend context entry pts encoding, also
> +	 * respect the soft pasid_max value set by the iommu.
> +	 * - number of PASID bits = ecap_pss + 1
> +	 * - number of PASID table entries = 2^(pts + 5)
> +	 * Therefore, pts = ecap_pss - 4
> +	 * e.g. KBL ecap_pss = 0x13, PASID has 20 bits, pts = 15
> +	 */
> +	if (ecap_pss(iommu->ecap) < 5)
> +		return 0;
> +
> +	/* pasid_max is encoded as actual number of entries not the bits */
> +	return find_first_bit((unsigned long *)&iommu->pasid_max,
> +			MAX_NR_PASID_BITS) - 5;
> +}
> +
>  int intel_iommu_enable_pasid(struct intel_iommu *iommu, struct intel_svm_dev *sdev)
>  {
>  	struct device_domain_info *info;
> @@ -5205,7 +5224,9 @@ int intel_iommu_enable_pasid(struct intel_iommu *iommu, struct intel_svm_dev *sd
>  
>  	if (!(ctx_lo & CONTEXT_PASIDE)) {
>  		context[1].hi = (u64)virt_to_phys(iommu->pasid_state_table);
> -		context[1].lo = (u64)virt_to_phys(iommu->pasid_table) | ecap_pss(iommu->ecap);
> +		context[1].lo = (u64)virt_to_phys(iommu->pasid_table) |
> +			intel_iommu_get_pts(iommu);
> +
>  		wmb();
>  		/* CONTEXT_TT_MULTI_LEVEL and CONTEXT_TT_DEV_IOTLB are both
>  		 * extended to permit requests-with-PASID if the PASIDE bit
> -- 
> 2.7.4