Re: [PATCH 1/1] iommu/vt-d: Avoid WARNING in sva unbind path

[Yi Liu]

On 5/19/26 13:29, Lu Baolu wrote:
> The Intel IOMMU driver allows SVA on devices even if they do not support
> PCI/PRI. Commit 39c20c4e83b9 ("iommu/vt-d: Only handle IOPF for SVA when
> PRI is supported") modified the SVA bind path to allow this configuration
> by skipping IOPF enablement when PRI is missing. However, it failed to
> update the unbind path.
>
> This creates an imbalance: the unbind path attempts to disable IOPF for
> a device that never had it enabled, triggering a WARNING in
> intel_iommu_disable_iopf():
>
>   WARNING: drivers/iommu/intel/iommu.c:3475 at intel_iommu_disable_iopf+0x4f/0x90d
>   Call Trace:
>    <TASK>
>    blocking_domain_set_dev_pasid+0x50/0x70
>    iommu_detach_device_pasid+0x89/0xc0
>    iommu_sva_unbind_device+0x73/0x150
>    xe_vm_close_and_put+0x4d2/0x1200 [xe]
>
> Fix this by bypassing IOPF operations for SVA domains on non-PRI hardware
> in both the bind and unbind paths.
>
> Fixes: 39c20c4e83b9 ("iommu/vt-d: Only handle IOPF for SVA when PRI is supported")
> Cc: stable@xxxxxxxxxxxxxxx
> Reported-by: Nareshkumar Gollakoti <naresh.kumar.g@xxxxxxxxx>
> Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> ---
>   drivers/iommu/intel/iommu.h | 11 +++++++++++
>   drivers/iommu/intel/svm.c   | 12 ++++--------
>   2 files changed, 15 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/iommu/intel/iommu.h b/drivers/iommu/intel/iommu.h
> index ef145560aa98..775f1c4ae346 100644
> --- a/drivers/iommu/intel/iommu.h
> +++ b/drivers/iommu/intel/iommu.h
> @@ -1254,18 +1254,29 @@ void intel_iommu_disable_iopf(struct device *dev);
>   static inline int iopf_for_domain_set(struct iommu_domain *domain,
>   				      struct device *dev)
>   {
> +	struct device_domain_info *info = dev_iommu_priv_get(dev);
> +
>   	if (!domain || !domain->iopf_handler)
>   		return 0;
>   
> +	/* SVA with non-IOMMU/PRI IOPF handling is allowed. */
> +	if (domain->type == IOMMU_DOMAIN_SVA && !info->pri_supported)
> +		return 0;
> +

Looked into the history a bit, and this story begins with commit
a86fb7717320 ("iommu/vt-d: Allow SVA with device-specific IOPF"). This
commit enabled devices that support their own IOPF mechanism to use SVA
even when the platform IOMMU doesn't support IOPF.

However, SVA isn't the only fault-capable domain type. Other fault-capable
domain types (e.g., paging domains) should also be able to leverage
device-specific IOPF capabilities.

My question is: can we drop the domain type check to support other types
of fault-capable domains that rely on device-specific IOPF?

Regards,
Yi Liu