Re: [PATCH v3 08/18] iommu/vt-d: clear unpreserved context entries during shutdown

[Baolu Lu <baolu.lu@linux.intel.com>]

On 6/15/26 07:37, 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 and root entries for the
> unpreserved context tables need to be cleared.
> 
> Signed-off-by: Samiullah Khawaja <skhawaja@google.com>
> ---
>   drivers/iommu/intel/iommu.c      |  9 ++--
>   drivers/iommu/intel/iommu.h      |  6 +++
>   drivers/iommu/intel/liveupdate.c | 74 ++++++++++++++++++++++++++++++++
>   3 files changed, 86 insertions(+), 3 deletions(-)

Please tweak the commit title to: "iommu/vt-d: Clear unpreserved..."
(capitalize "Clear") to match the driver's commit history style.

A high-level question: have you looked at how the suspend/resume path
behaves with the iommu and device preservation? DMA translation is
disabled and re-enabled there. I don't see any immediate changes are
needed there, but it would be good to call it out explicitly if it was
overlooked.

> 
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index 715b538e7efe..26258861e3bf 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -2374,8 +2374,11 @@ 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);
> +		/* Make sure the IOMMUs are switched off if not preserved. */
> +		if (iommu_preserved_state(&iommu->iommu))
> +			clear_unpreserved_context_entries(iommu);

How are PCI devices handled during a live update kexec? Do they go
through the standard iommu_release_device() path?

I assume they do not, because if they did, the context entries for
preserved devices could be updated after preservation. If they do bypass
the release_device path, why not just explicitly invoke
iommu_release_device() for all devices that are not preserved?

Using iommu_release_device() for the unpreserved devices would naturally
erase their context entries and securely park those devices in a DMA
blocking state.

> +		else
> +			iommu_disable_translation(iommu);
>   	}
>   }
> 

[...]

Thanks,
baolu