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

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Message-ID: <20240619151254.GI1091770@ziepe.ca>
Date: Wed, 19 Jun 2024 12:12:54 -0300
From: Jason Gunthorpe <jgg@...pe.ca>
To: Lu Baolu <baolu.lu@...ux.intel.com>
Cc: Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
	Robin Murphy <robin.murphy@....com>,
	Kevin Tian <kevin.tian@...el.com>, Yi Liu <yi.l.liu@...el.com>,
	David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
	Kalle Valo <kvalo@...nel.org>,
	Bjorn Andersson <andersson@...nel.org>,
	Mathieu Poirier <mathieu.poirier@...aro.org>,
	Alex Williamson <alex.williamson@...hat.com>, mst@...hat.com,
	Jason Wang <jasowang@...hat.com>,
	Thierry Reding <thierry.reding@...il.com>,
	Jonathan Hunter <jonathanh@...dia.com>,
	Mikko Perttunen <mperttunen@...dia.com>,
	Jeff Johnson <quic_jjohnson@...cinc.com>,
	ath10k@...ts.infradead.org, ath11k@...ts.infradead.org,
	iommu@...ts.linux.dev, dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 15/21] iommu/vt-d: Add helper to allocate paging domain

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@...ux.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@...dia.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