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[PATCH 1/6] VT-d: properly reserve DID 0 for caching mode IOMMUs
- To: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Fri, 12 Nov 2021 10:47:59 +0100
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- Cc: Kevin Tian <kevin.tian@xxxxxxxxx>
- Delivery-date: Fri, 12 Nov 2021 09:48:13 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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>
--- 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;
}
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