linux-kernel - Re: [PATCH v2] iommu/vt-d: Turn off translations at shutdown

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Date:   Mon, 11 Nov 2019 16:08:15 +0100
From:   Joerg Roedel <joro@...tes.org>
To:     Deepa Dinamani <deepa.kernel@...il.com>
Cc:     linux-kernel@...r.kernel.org, baolu.lu@...ux.intel.com,
        dwmw2@...radead.org, iommu@...ts.linux-foundation.org
Subject: Re: [PATCH v2] iommu/vt-d: Turn off translations at shutdown

On Sun, Nov 10, 2019 at 09:27:44AM -0800, Deepa Dinamani wrote:
> The intel-iommu driver assumes that the iommu state is
> cleaned up at the start of the new kernel.
> But, when we try to kexec boot something other than the
> Linux kernel, the cleanup cannot be relied upon.
> Hence, cleanup before we go down for reboot.
> 
> Keeping the cleanup at initialization also, in case BIOS
> leaves the IOMMU enabled.
> 
> I considered turning off iommu only during kexec reboot, but a clean
> shutdown seems always a good idea. But if someone wants to make it
> conditional, such as VMM live update, we can do that.  There doesn't
> seem to be such a condition at this time.
> 
> Tested that before, the info message
> 'DMAR: Translation was enabled for <iommu> but we are not in kdump mode'
> would be reported for each iommu. The message will not appear when the
> DMA-remapping is not enabled on entry to the kernel.
> 
> Signed-off-by: Deepa Dinamani <deepa.kernel@...il.com>
> ---
> Changes since v1:
> * move shutdown registration to iommu detection
> 
>  drivers/iommu/dmar.c        |  5 ++++-
>  drivers/iommu/intel-iommu.c | 20 ++++++++++++++++++++
>  include/linux/dmar.h        |  2 ++
>  3 files changed, 26 insertions(+), 1 deletion(-)

Applied, thanks.