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

Tian, Kevin
2022-05-10T00:51:58Z

> From: Lu Baolu <baolu.lu@linux.intel.com>
> 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@linux.intel.com>

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

> ---
> 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