Re: [PATCH 5/7] iommu/vt-d: Add helper to allocate paging domain

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

On 2024/7/2 21:08, Lu Baolu wrote:
> The domain_alloc_user operation is currently implemented by allocating a
> paging domain using iommu_domain_alloc(). This is because it needs to fully
> initialize the domain before return. Add a helper to do this to avoid using
> iommu_domain_alloc().
> 
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
> Link: https://lore.kernel.org/r/20240610085555.88197-16-baolu.lu@linux.intel.com
> ---
>   drivers/iommu/intel/iommu.c | 90 +++++++++++++++++++++++++++++++++----
>   1 file changed, 81 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index 1b5519dfa085..1f0d6892a0b6 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -3622,6 +3622,79 @@ static struct iommu_domain blocking_domain = {
>   	}
>   };
>   
> +static int iommu_superpage_capability(struct intel_iommu *iommu, bool first_stage)
> +{
> +	if (!intel_iommu_superpage)
> +		return 0;
> +
> +	if (first_stage)
> +		return cap_fl1gp_support(iommu->cap) ? 2 : 1;
> +
> +	return fls(cap_super_page_val(iommu->cap));
> +}
> +
> +static struct dmar_domain *paging_domain_alloc(struct device *dev, bool first_stage)
> +{
> +	struct device_domain_info *info = dev_iommu_priv_get(dev);
> +	struct intel_iommu *iommu = info->iommu;
> +	struct dmar_domain *domain;
> +	int addr_width;
> +
> +	domain = kzalloc(sizeof(*domain), GFP_KERNEL);
> +	if (!domain)
> +		return ERR_PTR(-ENOMEM);
> +
> +	INIT_LIST_HEAD(&domain->devices);
> +	INIT_LIST_HEAD(&domain->dev_pasids);
> +	INIT_LIST_HEAD(&domain->cache_tags);
> +	spin_lock_init(&domain->lock);
> +	spin_lock_init(&domain->cache_lock);
> +	xa_init(&domain->iommu_array);
> +
> +	domain->nid = dev_to_node(dev);
> +	domain->has_iotlb_device = info->ats_enabled;
> +	domain->use_first_level = first_stage;
> +
> +	/* calculate the address width */
> +	addr_width = agaw_to_width(iommu->agaw);
> +	if (addr_width > cap_mgaw(iommu->cap))
> +		addr_width = cap_mgaw(iommu->cap);
> +	domain->gaw = addr_width;
> +	domain->agaw = iommu->agaw;
> +	domain->max_addr = __DOMAIN_MAX_ADDR(addr_width);
> +
> +	/* iommu memory access coherency */
> +	domain->iommu_coherency = iommu_paging_structure_coherency(iommu);
> +
> +	/* pagesize bitmap */
> +	domain->domain.pgsize_bitmap = SZ_4K;
> +	domain->iommu_superpage = iommu_superpage_capability(iommu, first_stage);
> +	domain->domain.pgsize_bitmap |= domain_super_pgsize_bitmap(domain);
> +
> +	/*
> +	 * IOVA aperture: First-level translation restricts the input-address
> +	 * to a canonical address (i.e., address bits 63:N have the same value
> +	 * as address bit [N-1], where N is 48-bits with 4-level paging and
> +	 * 57-bits with 5-level paging). Hence, skip bit [N-1].
> +	 */
> +	domain->domain.geometry.force_aperture = true;
> +	domain->domain.geometry.aperture_start = 0;
> +	if (first_stage)
> +		domain->domain.geometry.aperture_end = __DOMAIN_MAX_ADDR(domain->gaw - 1);
> +	else
> +		domain->domain.geometry.aperture_end = __DOMAIN_MAX_ADDR(domain->gaw);
> +
> +	/* always allocate the top pgd */
> +	domain->pgd = iommu_alloc_page_node(domain->nid, GFP_KERNEL);
> +	if (!domain->pgd) {
> +		kfree(domain);
> +		return ERR_PTR(-ENOMEM);
> +	}
> +	domain_flush_cache(domain, domain->pgd, PAGE_SIZE);
> +
> +	return domain;
> +}
> +
>   static struct iommu_domain *intel_iommu_domain_alloc(unsigned type)
>   {
>   	struct dmar_domain *dmar_domain;
> @@ -3684,15 +3757,14 @@ intel_iommu_domain_alloc_user(struct device *dev, u32 flags,
>   	if (user_data || (dirty_tracking && !ssads_supported(iommu)))
>   		return ERR_PTR(-EOPNOTSUPP);
>   
> -	/*
> -	 * domain_alloc_user op needs to fully initialize a domain before
> -	 * return, so uses iommu_domain_alloc() here for simple.

I think it is still valuable to note the requirement of full initialize
a domain. is it? Otherwise, looks good to me.

Reviewed-by: Yi Liu <yi.l.liu@intel.com>

> -	 */
> -	domain = iommu_domain_alloc(dev->bus);
> -	if (!domain)
> -		return ERR_PTR(-ENOMEM);
> -
> -	dmar_domain = to_dmar_domain(domain);
> +	/* Do not use first stage for user domain translation. */
> +	dmar_domain = paging_domain_alloc(dev, false);
> +	if (IS_ERR(dmar_domain))
> +		return ERR_CAST(dmar_domain);
> +	domain = &dmar_domain->domain;
> +	domain->type = IOMMU_DOMAIN_UNMANAGED;
> +	domain->owner = &intel_iommu_ops;
> +	domain->ops = intel_iommu_ops.default_domain_ops;
>   
>   	if (nested_parent) {
>   		dmar_domain->nested_parent = true;

-- 
Regards,
Yi Liu