Re: [PATCH 06/14] iommu/vt-d: Implement device and iommu preserve/unpreserve ops

[Samiullah Khawaja]

On Thu, Mar 19, 2026 at 09:04:31AM -0700, Vipin Sharma wrote:
> On Tue, Feb 03, 2026 at 10:09:40PM +0000, Samiullah Khawaja wrote:
> >  /*
> >   * Take a root_entry and return the Lower Context Table Pointer (LCTP)
> >   * if marked present.
> > @@ -2378,8 +2379,10 @@ void intel_iommu_shutdown(void)
> >  		/* Disable PMRs explicitly here. */
> >  		iommu_disable_protect_mem_regions(iommu);
> >
> > -		/* Make sure the IOMMUs are switched off */
> > -		iommu_disable_translation(iommu);
> > +		if (!__maybe_clean_unpreserved_context_entries(iommu)) {
> > +			/* Make sure the IOMMUs are switched off */
> > +			iommu_disable_translation(iommu);
> > +		}
>
> I think instead of having a "maybe" function where it might or might not
> clear the context entry, it will be simpler to just make if-else
> explicit here.
>
> @@ -2375,8 +2375,11 @@ void intel_iommu_shutdown(void)
>                /* Disable PMRs explicitly here. */
>                iommu_disable_protect_mem_regions(iommu);
>
> -               /* Make sure the IOMMUs are switched off */
> -               iommu_disable_translation(iommu);
> +               if (iommu->iommu.outgoing_preserved_state)

This is only defined when CONFIG_LIVEUPDATE is enabled and would need
the #ifdefs :(.

But I can add a function, iommu_outgoing_preserved_state() or
iommu_is_outgoing_preserved() that would return NULL or false
respectively when liveupdate is disabled, in the skeleton patch to check
this.

I will update this in the next revision.
> +                       clear_unpreserved_context_entries();
> +               else
> +                       /* Make sure the IOMMUs are switched off */
> +                       iommu_disable_translation(iommu);
>        }
> }
>
> clear_unpreserved_context_entries() will explicitly do what
> __maybe_clean_unpreserved_context_entries() is doing.
>
> >  	}
> >  }
> >
> > @@ -2902,6 +2905,38 @@ static const struct iommu_dirty_ops intel_second_stage_dirty_ops = {
> >  	.set_dirty_tracking = intel_iommu_set_dirty_tracking,
> >  };
> >
> > +#ifdef CONFIG_IOMMU_LIVEUPDATE
> > +static bool __maybe_clean_unpreserved_context_entries(struct intel_iommu *iommu)
>
> Nit: s/clean/clear, this matches domain_context_clear().

Agreed.
> > +{
> > +	struct device_domain_info *info;
> > +	struct pci_dev *pdev = NULL;
> > +
> > +	if (!iommu->iommu.outgoing_preserved_state)
> > +		return false;
> > +
> > +	for_each_pci_dev(pdev) {
> > +		info = dev_iommu_priv_get(&pdev->dev);
> > +		if (!info)
> > +			continue;
> > +
> > +		if (info->iommu != iommu)
> > +			continue;
> > +
> > +		if (dev_iommu_preserved_state(&pdev->dev))
> > +			continue;
> > +
> > +		domain_context_clear(info);
> > +	}
> > +
> > +	return true;
> > +}
> > +++ b/drivers/iommu/intel/liveupdate.c
> > @@ -0,0 +1,134 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +
> > +/*
> > + * Copyright (C) 2025, Google LLC
> > + * Author: Samiullah Khawaja <skhawaja@xxxxxxxxxx>
> > + */
> > +
> > +#define pr_fmt(fmt)    "iommu: liveupdate: " fmt

> Should this be 'DMAR: liveupdate' to be consistent with other files in
> intel iommu?

Agreed. Will change.
> > +
> > +#include <linux/kexec_handover.h>
> > +#include <linux/liveupdate.h>
> > +#include <linux/iommu-lu.h>
> > +#include <linux/module.h>
> > +#include <linux/pci.h>
> > +
> > +#include "iommu.h"
> > +#include "../iommu-pages.h"
> > +
> > +static void unpreserve_iommu_context(struct intel_iommu *iommu, int end)
>
> Nit: Can this be unpreserve_iommu_context_table(), similar to existing
> free_context_table()? Same for corresponding preserve function

Agreed. I will change this.
> > +{
> > +	struct context_entry *context;
> > +	int i;
> > +
> > +	if (end < 0)
> > +		end = ROOT_ENTRY_NR;
>
> Can't we just pass ROOT_ENTRY_NR as end value instead of -1?

Yes, we can do that. Will update.
>

Thanks,
Sami