linux-kernel - Re: [RFC PATCH v2 21/32] iommu/vt-d: Clean the context entries of unpreserved devices

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Message-ID: <52bed033-fa16-4429-a1c6-d8f24961b5ef@linux.intel.com>
Date: Thu, 4 Dec 2025 14:28:25 +0800
From: Baolu Lu <baolu.lu@...ux.intel.com>
To: Samiullah Khawaja <skhawaja@...gle.com>,
 David Woodhouse <dwmw2@...radead.org>, Joerg Roedel <joro@...tes.org>,
 Will Deacon <will@...nel.org>, Pasha Tatashin <pasha.tatashin@...een.com>,
 Jason Gunthorpe <jgg@...pe.ca>, iommu@...ts.linux.dev
Cc: Robin Murphy <robin.murphy@....com>, Pratyush Yadav
 <pratyush@...nel.org>, Kevin Tian <kevin.tian@...el.com>,
 Alex Williamson <alex@...zbot.org>, linux-kernel@...r.kernel.org,
 Saeed Mahameed <saeedm@...dia.com>,
 Adithya Jayachandran <ajayachandra@...dia.com>,
 Parav Pandit <parav@...dia.com>, Leon Romanovsky <leonro@...dia.com>,
 William Tu <witu@...dia.com>, Vipin Sharma <vipinsh@...gle.com>,
 dmatlack@...gle.com, YiFei Zhu <zhuyifei@...gle.com>,
 Chris Li <chrisl@...nel.org>, praan@...gle.com
Subject: Re: [RFC PATCH v2 21/32] iommu/vt-d: Clean the context entries of
 unpreserved devices

On 12/3/25 07:02, Samiullah Khawaja wrote:
> During normal shutdown the iommu translation is disabled. Since the root
> table is preserved during live update, it needs to be cleaned up and the
> context entries of the unpreserved devices need to be cleared.
> 
> Signed-off-by: Samiullah Khawaja<skhawaja@...gle.com>
> ---
>   drivers/iommu/intel/iommu.c      | 33 ++++++++++++++++++++++++++++++--
>   drivers/iommu/intel/iommu.h      |  1 +
>   drivers/iommu/intel/liveupdate.c |  1 +
>   3 files changed, 33 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index 3f69a073b2d8..84fef81ecf4d 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -16,6 +16,7 @@
>   #include <linux/crash_dump.h>
>   #include <linux/dma-direct.h>
>   #include <linux/dmi.h>
> +#include <linux/iommu-lu.h>
>   #include <linux/memory.h>
>   #include <linux/pci.h>
>   #include <linux/pci-ats.h>
> @@ -52,6 +53,10 @@ static int rwbf_quirk;
>   
>   #define rwbf_required(iommu)	(rwbf_quirk || cap_rwbf((iommu)->cap))
>   
> +#ifdef CONFIG_LIVEUPDATE
> +static void __clean_unpreserved_context_entries(struct intel_iommu *iommu);
> +#endif
> +
>   /*
>    * set to 1 to panic kernel if can't successfully enable VT-d
>    * (used when kernel is launched w/ TXT)
> @@ -2376,8 +2381,12 @@ 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) {
> +			__clean_unpreserved_context_entries(iommu);
> +		} else {
> +			/* Make sure the IOMMUs are switched off */
> +			iommu_disable_translation(iommu);
> +		}
>   	}
>   }
>   
> @@ -2884,6 +2893,26 @@ static const struct iommu_dirty_ops intel_second_stage_dirty_ops = {
>   	.set_dirty_tracking = intel_iommu_set_dirty_tracking,
>   };
>   
> +static void __clean_unpreserved_context_entries(struct intel_iommu *iommu)
> +{
> +	struct device_domain_info *info;
> +	struct pci_dev *pdev = NULL;
> +
> +	for_each_pci_dev(pdev) {
> +		info = dev_iommu_priv_get(&pdev->dev);
> +		if (!info)
> +			continue;

I assume the per-device iommu private data is freed in the
release_device path, which runs before intel_iommu_shutdown(). If that
is the case, "info" would always be NULL here, resulting the subsequent
code dead code. Or not?

> +
> +		if (info->iommu != iommu)
> +			continue;
> +
> +		if (dev_iommu_preserved_state(&pdev->dev))
> +			continue;
> +
> +		domain_context_clear(info);
> +	}
> +}

Thanks,
baolu