intel-iommu: Unify hardware and software passthrough support

This makes the hardware passthrough mode work a lot more like the
software version, so that the behaviour of a kernel with 'iommu=pt'
is the same whether the hardware supports passthrough or not.

In particular:
 - We use a single si_domain for the pass-through devices.
 - 32-bit devices can be taken out of the pass-through domain so that
   they don't have to use swiotlb.
 - Devices will work again after being removed from a KVM guest.
 - A potential oops on OOM (in init_context_pass_through()) is fixed.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

1 files changed, 2 insertions, 3 deletions

diff --git a/arch/x86/kernel/pci-swiotlb.c b/arch/x86/kernel/pci-swiotlb.c
index 6af96ee44200..1e66b18f45cb 100644
--- a/arch/x86/kernel/pci-swiotlb.c
+++ b/arch/x86/kernel/pci-swiotlb.c
@@ -71,9 +71,8 @@ void __init pci_swiotlb_init(void)
 {
         /* don't initialize swiotlb if iommu=off (no_iommu=1) */
 #ifdef CONFIG_X86_64
-        if ((!iommu_detected && !no_iommu && max_pfn > MAX_DMA32_PFN) ||
-                iommu_pass_through)
-               swiotlb = 1;
+        if ((!iommu_detected && !no_iommu && max_pfn > MAX_DMA32_PFN))
+                swiotlb = 1;
 #endif
         if (swiotlb_force)
                 swiotlb = 1;