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

From: Liu, Yi L
Date: Thu Jul 02 2020 - 23:53:23 EST

> From: Alex Williamson <alex.williamson@xxxxxxxxxx>
> Sent: Friday, July 3, 2020 1:55 AM
>
> On Wed, 24 Jun 2020 01:55:15 -0700
> Liu Yi L <yi.l.liu@xxxxxxxxx> 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@xxxxxxxxx>
> > CC: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> > Cc: Alex Williamson <alex.williamson@xxxxxxxxxx>
> > Cc: Eric Auger <eric.auger@xxxxxxxxxx>
> > Cc: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx>
> > Cc: Joerg Roedel <joro@xxxxxxxxxx>
> > Cc: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> > Signed-off-by: Liu Yi L <yi.l.liu@xxxxxxxxx>
> > Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> > ---
> > 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 */