Re: [PATCH v3 15/21] iommu/vt-d: Add helper to allocate paging domain

Jason Gunthorpe
2024-06-19T15:12:59Z

On Mon, Jun 10, 2024 at 04:55:49PM +0800, 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>
> ---
> drivers/iommu/intel/iommu.c | 87 +++++++++++++++++++++++++++++++++----
> 1 file changed, 78 insertions(+), 9 deletions(-)

It seems Ok, but I have some small thoughts

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>

> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index 2e9811bf2a4e..ccde5f5972e4 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -3633,6 +3633,79 @@ 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);

You should probably split more, with an 'alloc struct dmar_domain'
function that can be used by SVA and others too.

> + 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);

Then some of this stuff is really just paging only. Like
SVA/identity/etc don't have pgszie and other things.

Jason