linux-kernel - Re: [PATCH 1/2] iommu/vt-d: Skip dev-iotlb flush for inaccessible PCIe device without scalable mode

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Message-Id: <20251211041741.2132-1-guojinhui.liam@bytedance.com>
Date: Thu, 11 Dec 2025 12:17:41 +0800
From: "Jinhui Guo" <guojinhui.liam@...edance.com>
To: <baolu.lu@...ux.intel.com>
Cc: <dwmw2@...radead.org>, <guojinhui.liam@...edance.com>, 
	<iommu@...ts.linux.dev>, <joro@...tes.org>, 
	<linux-kernel@...r.kernel.org>, <will@...nel.org>
Subject: Re: [PATCH 1/2] iommu/vt-d: Skip dev-iotlb flush for inaccessible PCIe device without scalable mode

On Thu, Dec 11, 2025 10:10:52AM +0800, Baolu Lu wrote:
> > Since __context_flush_dev_iotlb() is only called on
> > {attach,release}_dev paths (not hot), add pci_device_is_present()
> > there to skip inaccessible devices and avoid the hard-lock.
> > 
> > Fixes: 37764b952e1b ("iommu/vt-d: Global devTLB flush when present context entry changed")
> > Fixes: 81e921fd3216 ("iommu/vt-d: Fix NULL domain on device release")
>
> Cc: stable@...r.kernel.org
>
> > Signed-off-by: Jinhui Guo <guojinhui.liam@...edance.com>
> > ---
> >   drivers/iommu/intel/pasid.c | 11 +++++++++++
> >   1 file changed, 11 insertions(+)
> > 
> > diff --git a/drivers/iommu/intel/pasid.c b/drivers/iommu/intel/pasid.c
> > index 3e2255057079..b1e8eb6a6504 100644
> > --- a/drivers/iommu/intel/pasid.c
> > +++ b/drivers/iommu/intel/pasid.c
> > @@ -1099,9 +1099,20 @@ int intel_pasid_setup_sm_context(struct device *dev)
> >    */
> >   static void __context_flush_dev_iotlb(struct device_domain_info *info)
> >   {
> > +	struct pci_dev *pdev;
> > +
> >   	if (!info->ats_enabled)
> >   		return;
> >   
> > +	/*
> > +	 * Skip dev-IOTLB flush for inaccessible PCIe devices to prevent the
> > +	 * Intel IOMMU from waiting indefinitely for an ATS invalidation that
> > +	 * cannot complete.
> > +	 */
> > +	pdev = dev_is_pci(info->dev) ? to_pci_dev(info->dev) : NULL;
> > +	if (pdev && !pci_device_is_present(pdev))
> > +		return;
>
> Could simply be
>
>	if (dev_is_pci(info->dev) &&
>	    !pci_device_is_present(to_pci_dev(info->dev)))
>		return;
>
> ?
>
> > +
> >   	qi_flush_dev_iotlb(info->iommu, PCI_DEVID(info->bus, info->devfn),
> >   			   info->pfsid, info->ats_qdep, 0, MAX_AGAW_PFN_WIDTH);
> >   

> Thanks,
> baolu

Hi, baolu

Thanks for your time and suggestions.

I’ve sent v2 (https://lore.kernel.org/all/20251211035946.2071-1-guojinhui.liam@bytedance.com/)
with the following changes:

1. Simplified the pci_device_is_present() check in __context_flush_dev_iotlb().
2. Added Cc: stable@...r.kernel.org to both patches.

Best Regards,
Jinhui