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

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

[Jacob Pan]

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@linux.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
-- 
2.7.4

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

[Jacob Pan]

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@linux.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@linux.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]

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

[Joerg Roedel]

Hi Jacob,

On Thu, Dec 01, 2016 at 01:50:26PM -0800, Jacob Pan wrote:
> 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);

Iommu->max_pasid already depends on ecap_pss(), so I think it is
better to just calculate the pts value as ffs(iommu->max_pasid) - 5.
This way you don't need an extra function and have a simpler
calculation.


	Joerg

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

[Jacob Pan]

On Tue, 6 Dec 2016 17:31:11 +0100
Joerg Roedel <joro@8bytes.org> wrote:

> Hi Jacob,
> 
> On Thu, Dec 01, 2016 at 01:50:26PM -0800, Jacob Pan wrote:
> > 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);  
> 
> Iommu->max_pasid already depends on ecap_pss(), so I think it is
> better to just calculate the pts value as ffs(iommu->max_pasid) - 5.
> This way you don't need an extra function and have a simpler
> calculation.
> 
Good point. I will make the change. Still keeping the lower bond
sanity check to prevent insanely small pss.

I initially did the patch w/o knowing David's pasid_max patch in rc7.
I was under the impression that pasid_max is a temp solution until we
remove the requirement of contiguous memory allocation.

Thanks,

Jacob