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Date: Fri, 12 Jun 2026 09:34:11 -0500
From: Bjorn Helgaas <helgaas@kernel.org>
To: Pranjal Shrivastava <praan@google.com>
Cc: iommu@lists.linux.dev, linux-pci@vger.kernel.org,
	linux-kernel@vger.kernel.org, Joerg Roedel <joro@8bytes.org>,
	Will Deacon <will@kernel.org>, Robin Murphy <robin.murphy@arm.com>,
	Baolu Lu <baolu.lu@linux.intel.com>,
	Jason Gunthorpe <jgg@nvidia.com>, Kevin Tian <kevin.tian@intel.com>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Samiullah Khawaja <skhawaja@google.com>,
	Nicolin Chen <nicolinc@nvidia.com>
Subject: Re: [PATCH v8 1/4] PCI/ATS: Ensure pci_ats_supported() is PF-aware
 for VFs
Message-ID: <20260612143411.GA599201@bhelgaas>
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In-Reply-To: <20260604182116.3179005-2-praan@google.com>

On Thu, Jun 04, 2026 at 06:21:13PM +0000, Pranjal Shrivastava wrote:
> Update pci_ats_supported() to additionally check the associated PF's
> status when called on a VF. This ensures that PF-level quirks and
> untrusted status are correctly propagated to VFs, providing a robust
> support check that aligns with the kernel's PF-centric ATS configuration
> model and is immune to the timing of VF-specific fixups.
> 
> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
> Reviewed-by: Samiullah Khawaja <skhawaja@google.com>
> Reviewed-by: Nicolin Chen <nicolinc@nvidia.com>
> 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>

Acked-by: Bjorn Helgaas <bhelgaas@google.com>

This series looks like material for the IOMMU tree?  Let me know if
you prefer merging these via PCI.

> ---
>  drivers/pci/ats.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/ats.c b/drivers/pci/ats.c
> index 96efa00d9743..679a3c3c1d54 100644
> --- a/drivers/pci/ats.c
> +++ b/drivers/pci/ats.c
> @@ -40,10 +40,13 @@ void pci_ats_init(struct pci_dev *dev)
>   */
>  bool pci_ats_supported(struct pci_dev *dev)
>  {
> -	if (!dev->ats_cap)
> +	if (!dev->ats_cap || dev->untrusted)
>  		return false;
>  
> -	return (dev->untrusted == 0);
> +	if (dev->is_virtfn)
> +		return pci_ats_supported(pci_physfn(dev));
> +
> +	return true;
>  }
>  EXPORT_SYMBOL_GPL(pci_ats_supported);
>  
> -- 
> 2.54.0.1032.g2f8565e1d1-goog
>