Re: [PATCH v8 4/4] iommu/vt-d: Fail probe on ATS configuration failure

[Samiullah Khawaja <skhawaja@google.com>]

On Thu, Jun 04, 2026 at 06:21:16PM +0000, Pranjal Shrivastava wrote:
>Update the Intel VT-d driver to handle ATS configuration and enablement
>more strictly. Specifically, update the device probe to fail if
>pci_prepare_ats() returns an error. This ensures that any ATS-capable
>master reaching the attach phase is guaranteed to have a valid config.
>
>Additionally, update iommu_enable_pci_ats() to WARN() if pci_enable_ats
>fails. Since earlier checks in the probe phase preclude config-related
>failures, any failure during hardware enablement is considered a kernel
>bug.
>
>Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
>Reviewed-by: Kevin Tian <kevin.tian@intel.com>
>Signed-off-by: Pranjal Shrivastava <praan@google.com>
>---
> drivers/iommu/intel/iommu.c | 15 ++++++++++++---
> 1 file changed, 12 insertions(+), 3 deletions(-)
>
>diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
>index 849d06dfe1ae..f39451323553 100644
>--- a/drivers/iommu/intel/iommu.c
>+++ b/drivers/iommu/intel/iommu.c
>@@ -876,8 +876,14 @@ static void iommu_enable_pci_ats(struct device_domain_info *info)
> 	if (!pci_ats_page_aligned(pdev))
> 		return;
>
>-	if (!pci_enable_ats(pdev, VTD_PAGE_SHIFT))
>-		info->ats_enabled = 1;
>+	/*
>+	 * pci_enable_ats() should not fail here because earlier checks
>+	 * have already verified support and configuration.
>+	 */
>+	if (WARN_ON(pci_enable_ats(pdev, VTD_PAGE_SHIFT)))
>+		return;
>+
>+	info->ats_enabled = 1;
> }
>
> static void iommu_disable_pci_ats(struct device_domain_info *info)
>@@ -3292,7 +3298,10 @@ static struct iommu_device *intel_iommu_probe_device(struct device *dev)
>
> 	dev_iommu_priv_set(dev, info);
> 	if (pdev && pci_ats_supported(pdev)) {
>-		pci_prepare_ats(pdev, VTD_PAGE_SHIFT);
>+		ret = pci_prepare_ats(pdev, VTD_PAGE_SHIFT);
>+		if (ret)
>+			goto free;
>+
> 		ret = device_rbtree_insert(iommu, info);
> 		if (ret)
> 			goto free;
>-- 
>2.54.0.1032.g2f8565e1d1-goog
>

Reviewed-by: Samiullah Khawaja <skhawaja@google.com>