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

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Date:   Mon, 5 Dec 2016 22:40:35 -0800
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     LKML <linux-kernel@...r.kernel.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Joerg Roedel <joro@...tes.org>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>
Cc:     Raj Ashok <ashok.raj@...el.com>,
        Mika Kuoppala <mika.kuoppala@...ux.intel.com>,
        jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH] iommu/intel-iommu: fix pasid table size encoding

Hi David,

Any thoughts on this one? Without this patch Kabylake would fail with
IOMMU error when svm is initialized.

Thanks,

Jacob

On Thu,  1 Dec 2016 13:50:26 -0800
Jacob Pan <jacob.jun.pan@...ux.intel.com> wrote:

> 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.
> 
> Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> ---
>  drivers/iommu/intel-iommu.c | 27 ++++++++++++++++++++++++++-
>  1 file changed, 26 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index 27596e6..f112aa9 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -5173,6 +5173,29 @@ 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) +{
> +	unsigned long pts;
> +
> +	/*
> +	 * 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;
> +
> +	pts = (ecap_pss(iommu->ecap) - 4);
> +
> +	/* pasid_max is encoded as actual number of entries not the
> bits */
> +	return min(find_first_bit((unsigned long *)&iommu->pasid_max,
> +					MAX_NR_PASID_BITS) - 5, pts);
> +}
> +
>  int intel_iommu_enable_pasid(struct intel_iommu *iommu, struct
> intel_svm_dev *sdev) {
>  	struct device_domain_info *info;
> @@ -5205,7 +5228,9 @@ 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

[Jacob Pan]