RE: [PATCH v4 2/4] iommu/vt-d: Check domain force_snooping against attached devices

[Tian, Kevin]

> From: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> Sent: Sunday, May 8, 2022 8:35 PM
> 
> As domain->force_snooping only impacts the devices attached with the
> domain, there's no need to check against all IOMMU units. On the other
> hand, force_snooping could be set on a domain no matter whether it has
> been attached or not, and once set it is an immutable flag. If no
> device attached, the operation always succeeds. Then this empty domain
> can be only attached to a device of which the IOMMU supports snoop
> control.
> 
> Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>

Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>

> ---
>  include/linux/intel-iommu.h |  1 +
>  drivers/iommu/intel/pasid.h |  2 ++
>  drivers/iommu/intel/iommu.c | 53
> ++++++++++++++++++++++++++++++++++---
>  drivers/iommu/intel/pasid.c | 42 +++++++++++++++++++++++++++++
>  4 files changed, 95 insertions(+), 3 deletions(-)
> 
> diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
> index 72e5d7900e71..4f29139bbfc3 100644
> --- a/include/linux/intel-iommu.h
> +++ b/include/linux/intel-iommu.h
> @@ -540,6 +540,7 @@ struct dmar_domain {
>  	u8 has_iotlb_device: 1;
>  	u8 iommu_coherency: 1;		/* indicate coherency of
> iommu access */
>  	u8 force_snooping : 1;		/* Create IOPTEs with snoop control
> */
> +	u8 set_pte_snp:1;
> 
>  	struct list_head devices;	/* all devices' list */
>  	struct iova_domain iovad;	/* iova's that belong to this domain
> */
> diff --git a/drivers/iommu/intel/pasid.h b/drivers/iommu/intel/pasid.h
> index ab4408c824a5..583ea67fc783 100644
> --- a/drivers/iommu/intel/pasid.h
> +++ b/drivers/iommu/intel/pasid.h
> @@ -123,4 +123,6 @@ void intel_pasid_tear_down_entry(struct
> intel_iommu *iommu,
>  				 bool fault_ignore);
>  int vcmd_alloc_pasid(struct intel_iommu *iommu, u32 *pasid);
>  void vcmd_free_pasid(struct intel_iommu *iommu, u32 pasid);
> +void intel_pasid_setup_page_snoop_control(struct intel_iommu *iommu,
> +					  struct device *dev, u32 pasid);
>  #endif /* __INTEL_PASID_H */
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index b4802f4055a0..048ebfbd5fcb 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -2459,7 +2459,7 @@ static int domain_setup_first_level(struct
> intel_iommu *iommu,
>  	if (level == 5)
>  		flags |= PASID_FLAG_FL5LP;
> 
> -	if (domain->domain.type == IOMMU_DOMAIN_UNMANAGED)
> +	if (domain->force_snooping)
>  		flags |= PASID_FLAG_PAGE_SNOOP;
> 
>  	return intel_pasid_setup_first_level(iommu, dev, (pgd_t *)pgd, pasid,
> @@ -4444,7 +4444,7 @@ static int intel_iommu_map(struct iommu_domain
> *domain,
>  		prot |= DMA_PTE_READ;
>  	if (iommu_prot & IOMMU_WRITE)
>  		prot |= DMA_PTE_WRITE;
> -	if (dmar_domain->force_snooping)
> +	if (dmar_domain->set_pte_snp)
>  		prot |= DMA_PTE_SNP;
> 
>  	max_addr = iova + size;
> @@ -4567,13 +4567,60 @@ static phys_addr_t
> intel_iommu_iova_to_phys(struct iommu_domain *domain,
>  	return phys;
>  }
> 
> +static bool domain_support_force_snooping(struct dmar_domain *domain)
> +{
> +	struct device_domain_info *info;
> +	bool support = true;
> +
> +	assert_spin_locked(&device_domain_lock);
> +	list_for_each_entry(info, &domain->devices, link) {
> +		if (!ecap_sc_support(info->iommu->ecap)) {
> +			support = false;
> +			break;
> +		}
> +	}
> +
> +	return support;
> +}
> +
> +static void domain_set_force_snooping(struct dmar_domain *domain)
> +{
> +	struct device_domain_info *info;
> +
> +	assert_spin_locked(&device_domain_lock);
> +
> +	/*
> +	 * Second level page table supports per-PTE snoop control. The
> +	 * iommu_map() interface will handle this by setting SNP bit.
> +	 */
> +	if (!domain_use_first_level(domain)) {
> +		domain->set_pte_snp = true;
> +		return;
> +	}
> +
> +	list_for_each_entry(info, &domain->devices, link)
> +		intel_pasid_setup_page_snoop_control(info->iommu, info-
> >dev,
> +						     PASID_RID2PASID);
> +}
> +
>  static bool intel_iommu_enforce_cache_coherency(struct iommu_domain
> *domain)
>  {
>  	struct dmar_domain *dmar_domain = to_dmar_domain(domain);
> +	unsigned long flags;
> 
> -	if (!domain_update_iommu_snooping(NULL))
> +	if (dmar_domain->force_snooping)
> +		return true;
> +
> +	spin_lock_irqsave(&device_domain_lock, flags);
> +	if (!domain_support_force_snooping(dmar_domain)) {
> +		spin_unlock_irqrestore(&device_domain_lock, flags);
>  		return false;
> +	}
> +
> +	domain_set_force_snooping(dmar_domain);
>  	dmar_domain->force_snooping = true;
> +	spin_unlock_irqrestore(&device_domain_lock, flags);
> +
>  	return true;
>  }
> 
> diff --git a/drivers/iommu/intel/pasid.c b/drivers/iommu/intel/pasid.c
> index f8d215d85695..d19dd66a670c 100644
> --- a/drivers/iommu/intel/pasid.c
> +++ b/drivers/iommu/intel/pasid.c
> @@ -762,3 +762,45 @@ int intel_pasid_setup_pass_through(struct
> intel_iommu *iommu,
> 
>  	return 0;
>  }
> +
> +/*
> + * Set the page snoop control for a pasid entry which has been set up.
> + */
> +void intel_pasid_setup_page_snoop_control(struct intel_iommu *iommu,
> +					  struct device *dev, u32 pasid)
> +{
> +	struct pasid_entry *pte;
> +	u16 did;
> +
> +	spin_lock(&iommu->lock);
> +	pte = intel_pasid_get_entry(dev, pasid);
> +	if (WARN_ON(!pte || !pasid_pte_is_present(pte))) {
> +		spin_unlock(&iommu->lock);
> +		return;
> +	}
> +
> +	pasid_set_pgsnp(pte);
> +	did = pasid_get_domain_id(pte);
> +	spin_unlock(&iommu->lock);
> +
> +	if (!ecap_coherent(iommu->ecap))
> +		clflush_cache_range(pte, sizeof(*pte));
> +
> +	/*
> +	 * VT-d spec 3.4 table23 states guides for cache invalidation:
> +	 *
> +	 * - PASID-selective-within-Domain PASID-cache invalidation
> +	 * - PASID-selective PASID-based IOTLB invalidation
> +	 * - If (pasid is RID_PASID)
> +	 *    - Global Device-TLB invalidation to affected functions
> +	 *   Else
> +	 *    - PASID-based Device-TLB invalidation (with S=1 and
> +	 *      Addr[63:12]=0x7FFFFFFF_FFFFF) to affected functions
> +	 */
> +	pasid_cache_invalidation_with_pasid(iommu, did, pasid);
> +	qi_flush_piotlb(iommu, did, pasid, 0, -1, 0);
> +
> +	/* Device IOTLB doesn't need to be flushed in caching mode. */
> +	if (!cap_caching_mode(iommu->cap))
> +		devtlb_invalidation_with_pasid(iommu, dev, pasid);
> +}
> --
> 2.25.1