linux-kernel - Re: [PATCH v13 3/3] iommu/vt-d: improve ITE fault handling if target device isn't valid

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Date: Tue, 27 Feb 2024 07:54:06 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Ethan Zhao <haifeng.zhao@...ux.intel.com>
Cc: baolu.lu@...ux.intel.com, bhelgaas@...gle.com, robin.murphy@....com,
	jgg@...pe.ca, kevin.tian@...el.com, dwmw2@...radead.org,
	will@...nel.org, lukas@...ner.de, yi.l.liu@...el.com,
	iommu@...ts.linux.dev, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org
Subject: Re: [PATCH v13 3/3] iommu/vt-d: improve ITE fault handling if target
 device isn't valid

On Tue, Feb 27, 2024 at 04:00:33AM +0800, Ethan Zhao wrote:
> > +                       if (!dev || !dev_is_pci(dev))
> > +                               return -ETIMEDOUT;
> > +                       pdev = to_pci_dev(dev);
> > +                       if (!pci_device_is_present(pdev) &&
> > +                               ite_sid == pci_dev_id(pci_physfn(pdev)))
> >                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > Unless the device_rbtree_find() is returning garbage then these things
> > must be true.
> > 
> > +                               return -ETIMEDOUT;
> > 
> > I tried to double check how we were storing devices into the rbtree,
> > but then I discovered that the device_rbtree_find() doesn't exist in
> > linux-next and this patch breaks the build.
> > 
> > This is very frustrating thing.  But let's say a buggy BIOS could mess
> > up the rbtree.  In that situation, we would still want to change the &&
> > to an ||.  If the divice is not present and^W or the rbtree is corrupted
> 
> Maybe you meant
> +                       if (!pci_device_is_present(pdev) ||
> +                               ite_sid != pci_dev_id(pci_physfn(pdev)))

Yep, that's what I was asking.

> 
> Unfortunately, the ite_sid we got from the "Invalidation Queue Error Record Register" is the *PCI Requester-id* of faulty device, that could be different
> BDF as the sid in the ATS invalidation request for devices:
> 
> 1. behind the PCIe to PCI bridges.
> 2. behindConventional PCI Bridges  3.PCI Express* Devices Using Phantom
> Functions  4.Intel® Scalable I/O Virtualization Capable Devices  (e.g. ADI)
> 5. devices with ARI function.
> 6. behind root port without ACS enabled.
> ... ...

Fair enough...  Thanks.

regards,
dan carpenter