RE: [PATCH v6 15/15] iommu/vt-d: Support reporting nesting capability info

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

Eric,

> From: Auger Eric <eric.auger@redhat.com>
> Sent: Monday, August 17, 2020 3:43 PM
> 
> On 8/17/20 9:05 AM, Liu, Yi L wrote:
> > Hi Eric,
> >
> >> Auger Eric <eric.auger@redhat.com>
> >> Sent: Sunday, August 16, 2020 8:01 PM
> >>
> >> Hi Yi,
> >>
> >> On 7/28/20 8:27 AM, Liu Yi L wrote:
> >>> This patch reports nesting info, and only supports the case where all
> >>> the physical iomms have the same CAP/ECAP MASKS.
> >> s/iomms/iommus
> >
> > yep.
> >
> >>>
> >>> 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>
> >>> ---
> >>> v2 -> v3:
> >>> *) remove cap/ecap_mask in iommu_nesting_info.
> >>> ---
> >>>  drivers/iommu/intel/iommu.c | 81
> >> +++++++++++++++++++++++++++++++++++++++++++--
> >>>  include/linux/intel-iommu.h | 16 +++++++++
> >>>  2 files changed, 95 insertions(+), 2 deletions(-)
> >>>
> >>> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> >>> index 88f4647..0835804 100644
> >>> --- a/drivers/iommu/intel/iommu.c
> >>> +++ b/drivers/iommu/intel/iommu.c
> >>> @@ -5660,12 +5660,16 @@ static inline bool iommu_pasid_support(void)
> >>>  static inline bool nested_mode_support(void)
> >>>  {
> >>>  	struct dmar_drhd_unit *drhd;
> >>> -	struct intel_iommu *iommu;
> >>> +	struct intel_iommu *iommu, *prev = NULL;
> >>>  	bool ret = true;
> >>>
> >>>  	rcu_read_lock();
> >>>  	for_each_active_iommu(iommu, drhd) {
> >>> -		if (!sm_supported(iommu) || !ecap_nest(iommu->ecap)) {
> >>> +		if (!prev)
> >>> +			prev = iommu;
> >>> +		if (!sm_supported(iommu) || !ecap_nest(iommu->ecap) ||
> >>> +		    (VTD_CAP_MASK & (iommu->cap ^ prev->cap)) ||
> >>> +		    (VTD_ECAP_MASK & (iommu->ecap ^ prev->ecap))) {
> >>>  			ret = false;
> >>>  			break;
> >> So this changes the behavior of DOMAIN_ATTR_NESTING. Shouldn't it have a
> >> Fixes tag as well? And maybe add the capability getter in a separate patch?
> >
> > yes, this changed the behavior. so it would be better to be a separate patch
> > and upstream along? how about your idea? @Lu, Baolu :-)
> >
> >>>  		}
> >>> @@ -6081,6 +6085,78 @@ intel_iommu_domain_set_attr(struct
> iommu_domain
> >> *domain,
> >>>  	return ret;
> >>>  }
> >>>
> >>> +static int intel_iommu_get_nesting_info(struct iommu_domain *domain,
> >>> +					struct iommu_nesting_info *info)
> >>> +{
> >>> +	struct dmar_domain *dmar_domain = to_dmar_domain(domain);
> >>> +	u64 cap = VTD_CAP_MASK, ecap = VTD_ECAP_MASK;
> >>> +	struct device_domain_info *domain_info;
> >>> +	struct iommu_nesting_info_vtd vtd;
> >>> +	unsigned long flags;
> >>> +	unsigned int size;
> >>> +
> >
> > perhaps better to acquire the lock here. [1]
> >
> >>> +	if (domain->type != IOMMU_DOMAIN_UNMANAGED ||
> >>> +	    !(dmar_domain->flags & DOMAIN_FLAG_NESTING_MODE))
> >>> +		return -ENODEV;
> >>> +
> >>> +	if (!info)
> >>> +		return -EINVAL;
> >>> +
> >>> +	size = sizeof(struct iommu_nesting_info) +
> >>> +		sizeof(struct iommu_nesting_info_vtd);
> >>> +	/*
> >>> +	 * if provided buffer size is smaller than expected, should
> >>> +	 * return 0 and also the expected buffer size to caller.
> >>> +	 */
> >>> +	if (info->argsz < size) {
> >>> +		info->argsz = size;
> >>> +		return 0;
> >>> +	}
> >>> +
> >>> +	spin_lock_irqsave(&device_domain_lock, flags);
> >>> +	/*
> >>> +	 * arbitrary select the first domain_info as all nesting
> >>> +	 * related capabilities should be consistent across iommu
> >>> +	 * units.
> >>> +	 */
> >>> +	domain_info = list_first_entry(&dmar_domain->devices,
> >>> +				       struct device_domain_info, link);
> >>> +	cap &= domain_info->iommu->cap;
> >>> +	ecap &= domain_info->iommu->ecap;
> >>> +	spin_unlock_irqrestore(&device_domain_lock, flags);
> >>> +
> >>> +	info->format = IOMMU_PASID_FORMAT_INTEL_VTD;
> >>> +	info->features = IOMMU_NESTING_FEAT_SYSWIDE_PASID |
> >>> +			 IOMMU_NESTING_FEAT_BIND_PGTBL |
> >>> +			 IOMMU_NESTING_FEAT_CACHE_INVLD;
> >>> +	info->addr_width = dmar_domain->gaw;
> >>> +	info->pasid_bits = ilog2(intel_pasid_max_id);
> >>> +	info->padding = 0;
> >>> +	vtd.flags = 0;
> >>> +	vtd.padding = 0;
> >>> +	vtd.cap_reg = cap;
> >>> +	vtd.ecap_reg = ecap;
> >>> +
> >>> +	memcpy(info->data, &vtd, sizeof(vtd));
> >>> +	return 0;
> >>> +}
> >>> +
> >>> +static int intel_iommu_domain_get_attr(struct iommu_domain *domain,
> >>> +				       enum iommu_attr attr, void *data)
> >>> +{
> >>> +	switch (attr) {
> >>> +	case DOMAIN_ATTR_NESTING:
> >>> +	{
> >>> +		struct iommu_nesting_info *info =
> >>> +				(struct iommu_nesting_info *)data;
> >>
> >> don't you need to hold a device_domain_lock earlier to make sure domain
> >> attributes can't change behind your back (unmanaged type and nested mode)?
> >
> > do you mean acquire lock at [1]?
> yep either at [1] or before calling intel_iommu_get_nesting_info and
> adding a comment saying intel_iommu_get_nesting_info() shall be called
> with the lock held

will do. :-)

Regards,
Yi Liu

> Thanks
> 
> Eric
> >
> > Regards,
> > Yi Liu
> >
> >>> +
> >>> +		return intel_iommu_get_nesting_info(domain, info);
> >>> +	}
> >>> +	default:
> >>> +		return -ENOENT;
> >>> +	}
> >>> +}
> >>> +
> >>>  /*
> >>>   * Check that the device does not live on an external facing PCI port that is
> >>>   * marked as untrusted. Such devices should not be able to apply quirks and
> >>> @@ -6103,6 +6179,7 @@ const struct iommu_ops intel_iommu_ops = {
> >>>  	.domain_alloc		= intel_iommu_domain_alloc,
> >>>  	.domain_free		= intel_iommu_domain_free,
> >>>  	.domain_set_attr	= intel_iommu_domain_set_attr,
> >>> +	.domain_get_attr	= intel_iommu_domain_get_attr,
> >>>  	.attach_dev		= intel_iommu_attach_device,
> >>>  	.detach_dev		= intel_iommu_detach_device,
> >>>  	.aux_attach_dev		= intel_iommu_aux_attach_device,
> >>> diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
> >>> index f98146b..5acf795 100644
> >>> --- a/include/linux/intel-iommu.h
> >>> +++ b/include/linux/intel-iommu.h
> >>> @@ -197,6 +197,22 @@
> >>>  #define ecap_max_handle_mask(e) ((e >> 20) & 0xf)
> >>>  #define ecap_sc_support(e)	((e >> 7) & 0x1) /* Snooping Control */
> >>>
> >>> +/* Nesting Support Capability Alignment */
> >>> +#define VTD_CAP_FL1GP		BIT_ULL(56)
> >>> +#define VTD_CAP_FL5LP		BIT_ULL(60)
> >>> +#define VTD_ECAP_PRS		BIT_ULL(29)
> >>> +#define VTD_ECAP_ERS		BIT_ULL(30)
> >>> +#define VTD_ECAP_SRS		BIT_ULL(31)
> >>> +#define VTD_ECAP_EAFS		BIT_ULL(34)
> >>> +#define VTD_ECAP_PASID		BIT_ULL(40)
> >>> +
> >>> +/* Only capabilities marked in below MASKs are reported */
> >>> +#define VTD_CAP_MASK		(VTD_CAP_FL1GP | VTD_CAP_FL5LP)
> >>> +
> >>> +#define VTD_ECAP_MASK		(VTD_ECAP_PRS | VTD_ECAP_ERS | \
> >>> +				 VTD_ECAP_SRS | VTD_ECAP_EAFS | \
> >>> +				 VTD_ECAP_PASID)
> >>> +
> >>>  /* Virtual command interface capability */
> >>>  #define vccap_pasid(v)		(((v) & DMA_VCS_PAS)) /* PASID allocation
> >> */
> >>>
> >>>
> >> Thanks
> >>
> >> Eric
> >

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