Re: [PATCH] iommu: Update "iommu.strict" documentation

[Lu Baolu]

On 6/14/21 10:57 PM, Robin Murphy wrote:
> Consolidating the flush queue logic also meant that the "iommu.strict"
> option started taking effect on x86 as well. Make sure we document that.
>
> Fixes: a250c23f15c2 ("iommu: remove DOMAIN_ATTR_DMA_USE_FLUSH_QUEUE")
> Signed-off-by: Robin Murphy <robin.murphy@xxxxxxx>
> ---
>   Documentation/admin-guide/kernel-parameters.txt | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index cb89dbdedc46..20a32de990ed 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -1987,7 +1987,7 @@
>   			  forcing Dual Address Cycle for PCI cards supporting
>   			  greater than 32-bit addressing.
>   
> -	iommu.strict=	[ARM64] Configure TLB invalidation behaviour
> +	iommu.strict=	[ARM64, X86] Configure TLB invalidation behaviour
>   			Format: { "0" | "1" }
>   			0 - Lazy mode.
>   			  Request that DMA unmap operations use deferred
> @@ -1998,6 +1998,10 @@
>   			1 - Strict mode (default).
>   			  DMA unmap operations invalidate IOMMU hardware TLBs
>   			  synchronously.
> +			Note: on x86, the default behaviour depends on the
> +			equivalent driver-specific parameters, but a strict
> +			mode explicitly specified by either method takes
> +			precedence.
>   
>   	iommu.passthrough=
>   			[ARM64, X86] Configure DMA to bypass the IOMMU by default.

Reviewed-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>

Best regards,
baolu