On 8/19/19 8:22 AM, Joerg Roedel wrote:
> From: Joerg Roedel <jroedel@xxxxxxx>
>
> Using Passthrough mode when SME is active causes certain
> devices to use the SWIOTLB bounce buffer. The bounce buffer
> code has an upper limit of 256kb for the size of DMA
> allocations, which is too small for certain devices and
> causes them to fail.
>
> With this patch we enable IOMMU by default when SME is
> active in the system, making the default configuration work
> for more systems than it does now.
>
> Users that don't want IOMMUs to be enabled still can disable
> them with kernel parameters.
>
> Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>
Reviewed-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
Tested-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
> ---
> drivers/iommu/iommu.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 01759d4ac70b..ec18c9630e93 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -119,6 +119,11 @@ static int __init iommu_subsys_init(void)
> iommu_set_default_passthrough(false);
> else
> iommu_set_default_translated(false);
> +
> + if (iommu_default_passthrough() && sme_active()) {
> + pr_info("SME detected - Disabling default IOMMU Passthrough\n");
> + iommu_set_default_translated(false);
> + }
> }
>
> pr_info("Default domain type: %s %s\n",
>
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