linux-kernel - Re: [PATCH] iommu: fix amd_iommu=force

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Date:   Wed, 5 Dec 2018 17:09:55 +0100
From:   Joerg Roedel <joro@...tes.org>
To:     Yu Zhao <yuzhao@...gle.com>
Cc:     iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iommu: fix amd_iommu=force_isolation

On Tue, Dec 04, 2018 at 03:37:16PM -0700, Yu Zhao wrote:
> The parameter is still there but it's ignored. We need to check its
> value before deciding to go into passthrough mode for AMD IOMMU.
> 
> Fixes: aafd8ba0ca74 ("iommu/amd: Implement add_device and remove_device")
> 
> Signed-off-by: Yu Zhao <yuzhao@...gle.com>
> ---
>  drivers/iommu/amd_iommu.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
> index 1167ff0416cf..3e4219e6cff0 100644
> --- a/drivers/iommu/amd_iommu.c
> +++ b/drivers/iommu/amd_iommu.c
> @@ -2195,7 +2195,8 @@ static int amd_iommu_add_device(struct device *dev)
>  
>  	BUG_ON(!dev_data);
>  
> -	if (iommu_pass_through || dev_data->iommu_v2)
> +	if (iommu_pass_through ||
> +	    (!amd_iommu_force_isolation && dev_data->iommu_v2))

This breaks the iommu_v2 use-case, as it needs a direct mapping for the
devices that support it.

I think the force_isolation parameter does not make sense anymore today
and should be removed.


Regards,

	Joerg