KVM: IOMMU: Disable device assignment without interrupt remapping
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>
diff --git a/virt/kvm/iommu.c b/virt/kvm/iommu.c
index 62a9caf..78c80f6 100644
--- a/virt/kvm/iommu.c
+++ b/virt/kvm/iommu.c
@@ -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 @@
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;