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KVM: IOMMU: Disable device assignment without interrupt remapping

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IOMMU interrupt remapping support provides a further layer of
isolation for device assignment by preventing arbitrary interrupt
block DMA writes by a malicious guest from reaching the host.  By
default, we should require that the platform provides interrupt
remapping support, with an opt-in mechanism for existing behavior.

Both AMD IOMMU and Intel VT-d2 hardware support interrupt
remapping, however we currently only have software support on
the Intel side.  Users wishing to re-enable device assignment
when interrupt remapping is not supported on the platform can
use the "allow_unsafe_assigned_interrupts=1" module option.

[avi: break long lines]

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Alex Williamson 2011-07-14 13:27:03 -06:00 committed by Avi Kivity
parent 4f0226482d
commit 3f68b0318b
1 changed files with 18 additions and 0 deletions
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18
virt/kvm/iommu.c
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@ -30,6 +30,12 @@
#include <linux/iommu.h>
#include <linux/intel-iommu.h>
static int allow_unsafe_assigned_interrupts;
module_param_named(allow_unsafe_assigned_interrupts,
allow_unsafe_assigned_interrupts, bool, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(allow_unsafe_assigned_interrupts,
"Enable device assignment on platforms without interrupt remapping support.");
static int kvm_iommu_unmap_memslots(struct kvm *kvm);
static void kvm_iommu_put_pages(struct kvm *kvm,
gfn_t base_gfn, unsigned long npages);
@ -231,6 +237,18 @@ int kvm_iommu_map_guest(struct kvm *kvm)
if (!kvm->arch.iommu_domain)
return -ENOMEM;
if (!allow_unsafe_assigned_interrupts &&
!iommu_domain_has_cap(kvm->arch.iommu_domain,
IOMMU_CAP_INTR_REMAP)) {
printk(KERN_WARNING "%s: No interrupt remapping support,"
" disallowing device assignment."
" Re-enble with \"allow_unsafe_assigned_interrupts=1\""
" module option.\n", __func__);
iommu_domain_free(kvm->arch.iommu_domain);
kvm->arch.iommu_domain = NULL;
return -EPERM;
}
r = kvm_iommu_map_memslots(kvm);
if (r)
goto out_unmap;