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RE: [PATCH 1/6] VT-d: properly reserve DID 0 for caching mode IOMMUs
- To: Jan Beulich <jbeulich@xxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: "Tian, Kevin" <kevin.tian@xxxxxxxxx>
- Date: Mon, 15 Nov 2021 05:13:54 +0000
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- Delivery-date: Mon, 15 Nov 2021 05:14:04 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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- Thread-topic: [PATCH 1/6] VT-d: properly reserve DID 0 for caching mode IOMMUs
> From: Jan Beulich <jbeulich@xxxxxxxx>
> Sent: Friday, November 12, 2021 5:48 PM
>
> Merely setting bit 0 in the bitmap is insufficient, as then Dom0 will
> still have DID 0 allocated to it, because of the zero-filling of
> domid_map[]. Set slot 0 to DOMID_INVALID to keep DID 0 from getting
> used.
>
> Fixes: b9c20c78789f ("VT-d: per-iommu domain-id")
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
>
> --- a/xen/drivers/passthrough/vtd/iommu.c
> +++ b/xen/drivers/passthrough/vtd/iommu.c
> @@ -1257,16 +1257,19 @@ int __init iommu_alloc(struct acpi_drhd_
> if ( !iommu->domid_bitmap )
> return -ENOMEM;
>
> + iommu->domid_map = xzalloc_array(u16, nr_dom);
> + if ( !iommu->domid_map )
> + return -ENOMEM;
> +
> /*
> - * if Caching mode is set, then invalid translations are tagged with
> - * domain id 0, Hence reserve bit 0 for it
> + * If Caching mode is set, then invalid translations are tagged with
> + * domain id 0. Hence reserve bit/slot 0.
> */
> if ( cap_caching_mode(iommu->cap) )
> + {
> + iommu->domid_map[0] = DOMID_INVALID;
> __set_bit(0, iommu->domid_bitmap);
> -
> - iommu->domid_map = xzalloc_array(u16, nr_dom);
> - if ( !iommu->domid_map )
> - return -ENOMEM;
> + }
>
> return 0;
> }
|
