linux-kernel - Re: [PATCH v7 03/10] iommu: Add attach handle to struct iopf

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Date: Fri, 28 Jun 2024 17:48:44 -0300
From: Jason Gunthorpe <jgg@...pe.ca>
To: Lu Baolu <baolu.lu@...ux.intel.com>
Cc: Kevin Tian <kevin.tian@...el.com>, Joerg Roedel <joro@...tes.org>,
	Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
	Jean-Philippe Brucker <jean-philippe@...aro.org>,
	Nicolin Chen <nicolinc@...dia.com>, Yi Liu <yi.l.liu@...el.com>,
	Jacob Pan <jacob.jun.pan@...ux.intel.com>,
	Joel Granados <j.granados@...sung.com>, iommu@...ts.linux.dev,
	virtualization@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 03/10] iommu: Add attach handle to struct iopf_group

On Sun, Jun 16, 2024 at 02:11:48PM +0800, Lu Baolu wrote:
> Previously, the domain that a page fault targets is stored in an
> iopf_group, which represents a minimal set of page faults. With the
> introduction of attach handle, replace the domain with the handle
> so that the fault handler can obtain more information as needed
> when handling the faults.
> 
> iommu_report_device_fault() is currently used for SVA page faults,
> which handles the page fault in an internal cycle. The domain is retrieved
> with iommu_get_domain_for_dev_pasid() if the pasid in the fault message
> is valid. This doesn't work in IOMMUFD case, where if the pasid table of
> a device is wholly managed by user space, there is no domain attached to
> the PASID of the device, and all page faults are forwarded through a
> NESTING domain attaching to RID.
> 
> Add a new IOMMU capability flag, IOMMU_CAP_USER_IOASID_TABLE, which
> indicates if the IOMMU driver supports user-managed PASID tables. In the
> iopf deliver path, if no attach handle found for the iopf PASID, roll
> back to RID domain when the IOMMU driver supports this capability.

This remark is out of date since it is now:

> @@ -547,6 +547,10 @@ static inline int __iommu_copy_struct_from_user_array(
>   * @default_domain: If not NULL this will always be set as the default domain.
>   *                  This should be an IDENTITY/BLOCKED/PLATFORM domain.
>   *                  Do not use in new drivers.
> + * @user_pasid_table: IOMMU driver supports user-managed PASID table. There is
> + *                    no user domain for each PASID and the I/O page faults are
> + *                    forwarded through the user domain attached to the device
> + *                    RID.
>   */
>  struct iommu_ops {
>  	bool (*capable)(struct device *dev, enum iommu_cap);
> @@ -590,6 +594,7 @@ struct iommu_ops {
>  	struct iommu_domain *blocked_domain;
>  	struct iommu_domain *release_domain;
>  	struct iommu_domain *default_domain;
> +	u8 user_pasid_table:1;
>  };

Otherwise looks goot

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

Jason