RE: [PATCH v3 02/14] iommu: Report domain nesting info

["Liu, Yi L" <yi.l.liu@intel.com>]

> From: Alex Williamson <alex.williamson@redhat.com>
> Sent: Friday, July 3, 2020 1:55 AM
> 
> On Wed, 24 Jun 2020 01:55:15 -0700
> Liu Yi L <yi.l.liu@intel.com> wrote:
> 
> > IOMMUs that support nesting translation needs report the capability
> > info to userspace, e.g. the format of first level/stage paging structures.
> >
> > This patch reports nesting info by DOMAIN_ATTR_NESTING. Caller can get
> > nesting info after setting DOMAIN_ATTR_NESTING.
> >
> > v2 -> v3:
> > *) remvoe cap/ecap_mask in iommu_nesting_info.
> > *) reuse DOMAIN_ATTR_NESTING to get nesting info.
> > *) return an empty iommu_nesting_info for SMMU drivers per Jean'
> >    suggestion.
> >
> > Cc: Kevin Tian <kevin.tian@intel.com>
> > CC: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > Cc: Alex Williamson <alex.williamson@redhat.com>
> > Cc: Eric Auger <eric.auger@redhat.com>
> > Cc: Jean-Philippe Brucker <jean-philippe@linaro.org>
> > Cc: Joerg Roedel <joro@8bytes.org>
> > Cc: Lu Baolu <baolu.lu@linux.intel.com>
> > Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
> > Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > ---
> >  drivers/iommu/arm-smmu-v3.c | 29 ++++++++++++++++++++--
> >  drivers/iommu/arm-smmu.c    | 29 ++++++++++++++++++++--
> >  include/uapi/linux/iommu.h  | 59
> > +++++++++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 113 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
> > index f578677..0c45d4d 100644
> > --- a/drivers/iommu/arm-smmu-v3.c
> > +++ b/drivers/iommu/arm-smmu-v3.c
> > @@ -3019,6 +3019,32 @@ static struct iommu_group
> *arm_smmu_device_group(struct device *dev)
> >  	return group;
> >  }
> >
> > +static int arm_smmu_domain_nesting_info(struct arm_smmu_domain
> *smmu_domain,
> > +					void *data)
> > +{
> > +	struct iommu_nesting_info *info = (struct iommu_nesting_info *) data;
> > +	u32 size;
> > +
> > +	if (!info || smmu_domain->stage != ARM_SMMU_DOMAIN_NESTED)
> > +		return -ENODEV;
> > +
> > +	size = sizeof(struct iommu_nesting_info);
> > +
> > +	/*
> > +	 * if provided buffer size is not equal to the size, should
> > +	 * return 0 and also the expected buffer size to caller.
> > +	 */
> > +	if (info->size != size) {
> > +		info->size = size;
> > +		return 0;
> > +	}
> > +
> > +	/* report an empty iommu_nesting_info for now */
> > +	memset(info, 0x0, size);
> > +	info->size = size;
> > +	return 0;
> > +}
> > +
> >  static int arm_smmu_domain_get_attr(struct iommu_domain *domain,
> >  				    enum iommu_attr attr, void *data)  { @@ -
> 3028,8 +3054,7 @@
> > static int arm_smmu_domain_get_attr(struct iommu_domain *domain,
> >  	case IOMMU_DOMAIN_UNMANAGED:
> >  		switch (attr) {
> >  		case DOMAIN_ATTR_NESTING:
> > -			*(int *)data = (smmu_domain->stage ==
> ARM_SMMU_DOMAIN_NESTED);
> > -			return 0;
> > +			return arm_smmu_domain_nesting_info(smmu_domain,
> data);
> >  		default:
> >  			return -ENODEV;
> >  		}
> > diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c index
> > 243bc4c..908607d 100644
> > --- a/drivers/iommu/arm-smmu.c
> > +++ b/drivers/iommu/arm-smmu.c
> > @@ -1506,6 +1506,32 @@ static struct iommu_group
> *arm_smmu_device_group(struct device *dev)
> >  	return group;
> >  }
> >
> > +static int arm_smmu_domain_nesting_info(struct arm_smmu_domain
> *smmu_domain,
> > +					void *data)
> > +{
> > +	struct iommu_nesting_info *info = (struct iommu_nesting_info *) data;
> > +	u32 size;
> > +
> > +	if (!info || smmu_domain->stage != ARM_SMMU_DOMAIN_NESTED)
> > +		return -ENODEV;
> > +
> > +	size = sizeof(struct iommu_nesting_info);
> > +
> > +	/*
> > +	 * if provided buffer size is not equal to the size, should
> > +	 * return 0 and also the expected buffer size to caller.
> > +	 */
> > +	if (info->size != size) {
> > +		info->size = size;
> > +		return 0;
> > +	}
> > +
> > +	/* report an empty iommu_nesting_info for now */
> > +	memset(info, 0x0, size);
> > +	info->size = size;
> > +	return 0;
> > +}
> > +
> >  static int arm_smmu_domain_get_attr(struct iommu_domain *domain,
> >  				    enum iommu_attr attr, void *data)  { @@ -
> 1515,8 +1541,7 @@
> > static int arm_smmu_domain_get_attr(struct iommu_domain *domain,
> >  	case IOMMU_DOMAIN_UNMANAGED:
> >  		switch (attr) {
> >  		case DOMAIN_ATTR_NESTING:
> > -			*(int *)data = (smmu_domain->stage ==
> ARM_SMMU_DOMAIN_NESTED);
> > -			return 0;
> > +			return arm_smmu_domain_nesting_info(smmu_domain,
> data);
> >  		default:
> >  			return -ENODEV;
> >  		}
> > diff --git a/include/uapi/linux/iommu.h b/include/uapi/linux/iommu.h
> > index 1afc661..898c99a 100644
> > --- a/include/uapi/linux/iommu.h
> > +++ b/include/uapi/linux/iommu.h
> > @@ -332,4 +332,63 @@ struct iommu_gpasid_bind_data {
> >  	} vendor;
> >  };
> >
> > +/*
> > + * struct iommu_nesting_info - Information for nesting-capable IOMMU.
> > + *				user space should check it before using
> > + *				nesting capability.
> > + *
> > + * @size:	size of the whole structure
> > + * @format:	PASID table entry format, the same definition with
> > + *		@format of struct iommu_gpasid_bind_data.
> > + * @features:	supported nesting features.
> > + * @flags:	currently reserved for future extension.
> > + * @data:	vendor specific cap info.
> > + *
> > + * +---------------+----------------------------------------------------+
> > + * | feature       |  Notes                                             |
> > + *
> >
> ++===============+============================================
> ========
> > ++
> > + * | SYSWIDE_PASID |  Kernel manages PASID in system wide, PASIDs used  |
> > + * |               |  in the system should be allocated by host kernel  |
> > + * +---------------+----------------------------------------------------+
> > + * | BIND_PGTBL    |  bind page tables to host PASID, the PASID could   |
> > + * |               |  either be a host PASID passed in bind request or  |
> > + * |               |  default PASIDs (e.g. default PASID of aux-domain) |
> > + * +---------------+----------------------------------------------------+
> > + * | CACHE_INVLD   |  mandatory feature for nesting capable IOMMU       |
> > + *
> > ++---------------+----------------------------------------------------
> > ++
> 
> Agree with the previous comments on these descriptions and Kevin's suggestions.

I see. will follow the suggestions.

> > + *
> > + */
> > +struct iommu_nesting_info {
> > +	__u32	size;
> > +	__u32	format;
> > +	__u32	features;
> > +#define IOMMU_NESTING_FEAT_SYSWIDE_PASID	(1 << 0)
> > +#define IOMMU_NESTING_FEAT_BIND_PGTBL		(1 << 1)
> > +#define IOMMU_NESTING_FEAT_CACHE_INVLD		(1 << 2)
> > +	__u32	flags;
> > +	__u8	data[];
> 
> How does the user determine which vendor structure is provided in data[]?

it can be deduced by the @format field. @format field follows the definition
in the iommu_gpasid_bind_data.

struct iommu_gpasid_bind_data {
        __u32 argsz;
#define IOMMU_GPASID_BIND_VERSION_1     1
        __u32 version;
#define IOMMU_PASID_FORMAT_INTEL_VTD    1
        __u32 format;
#define IOMMU_SVA_GPASID_VAL    (1 << 0) /* guest PASID valid */
        __u64 flags;
        __u64 gpgd;
        __u64 hpasid;
        __u64 gpasid;
        __u32 addr_width;
        __u8  padding[12];
        /* Vendor specific data */
        union {
                struct iommu_gpasid_bind_data_vtd vtd;
        } vendor;
};

Regards,
Yi Liu

> Thanks,
> 
> Alex
> 
> > +};
> > +
> > +/*
> > + * struct iommu_nesting_info_vtd - Intel VT-d specific nesting info
> > + *
> > + *
> > + * @flags:	VT-d specific flags. Currently reserved for future
> > + *		extension.
> > + * @addr_width:	The output addr width of first level/stage translation
> > + * @pasid_bits:	Maximum supported PASID bits, 0 represents no PASID
> > + *		support.
> > + * @cap_reg:	Describe basic capabilities as defined in VT-d capability
> > + *		register.
> > + * @ecap_reg:	Describe the extended capabilities as defined in VT-d
> > + *		extended capability register.
> > + */
> > +struct iommu_nesting_info_vtd {
> > +	__u32	flags;
> > +	__u16	addr_width;
> > +	__u16	pasid_bits;
> > +	__u64	cap_reg;
> > +	__u64	ecap_reg;
> > +};
> > +
> >  #endif /* _UAPI_IOMMU_H */