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SubjectRe: [PATCH] iommu/amd: Fix amd_iommu_detect() (does not fix any issues).
On Mon, Aug 31, 2015 at 06:13:03PM -0400, j.glisse@gmail.com wrote:
> From: Jérôme Glisse <jglisse@redhat.com>
>
> Fix amd_iommu_detect() to return positive value on success, like
> intended, and not zero. This will not change anything in the end
> as AMD IOMMU disable swiotlb and properly associate itself with

Not sure how it disables SWIOTLB? The AMD Vi does not seem to
change 'swiotlb'. While 'gart_iommu_init' does. Did you mean
the AMD GART code?

> devices even if detect() doesn't return a positive value.

Returning positive will mean that the pci_iommu_alloc will stop
processing _all_ other IOMMUs.

While returning 0 will let it detect the other IOMMUs.

Granted on an AMD machine there can be two 'IOMMU's - the GART
and the AMD Vi. The detection is always to call gart_iommu_hole_init
first, then amd_iommu_detect.

I presume if there was one more type on AMD we would run into trouble.


>
> Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
> Cc: Joerg Roedel <jroedel@suse.de>
> Cc: iommu@lists.linux-foundation.org
> ---
> drivers/iommu/amd_iommu_init.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/amd_iommu_init.c b/drivers/iommu/amd_iommu_init.c
> index a24495e..360a451 100644
> --- a/drivers/iommu/amd_iommu_init.c
> +++ b/drivers/iommu/amd_iommu_init.c
> @@ -2198,7 +2198,7 @@ int __init amd_iommu_detect(void)
> iommu_detected = 1;
> x86_init.iommu.iommu_init = amd_iommu_init;
>
> - return 0;
> + return 1;
> }
>
> /****************************************************************************
> --
> 1.8.3.1
>
> _______________________________________________
> iommu mailing list
> iommu@lists.linux-foundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/iommu


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