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

[Vipin Sharma]

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)
+                       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().

> +{
> +	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?

> +
> +#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

> +{
> +	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?