Re: [PATCH 4/5] iommu/vt-d: Disallow SVA if devices don't support 64-bit address

From: Lu Baolu
Date: Tue Jul 20 2021 - 21:53:43 EST

Hi Robin,

Thanks a lot for reviewing my patch!

On 7/20/21 5:27 PM, Robin Murphy wrote:
On 2021-07-20 02:38, Lu Baolu wrote:
When the device and CPU share an address space (such as SVA), the device
must support the same addressing capability as the CPU. The CPU does not
consider the addressing ability of any device when managing the page table
of a process, so the device must have enough addressing ability to bind
the page table of the process.

Signed-off-by: Lu Baolu <>
  drivers/iommu/intel/iommu.c | 3 +++
  1 file changed, 3 insertions(+)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index f45c80ce2381..f3cca1dd384d 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -5372,6 +5372,9 @@ static int intel_iommu_enable_sva(struct device *dev)
      if (!(iommu->flags & VTD_FLAG_SVM_CAPABLE))
          return -ENODEV;
+    if (!dev->dma_mask || *dev->dma_mask != DMA_BIT_MASK(64))

Careful - VFIO doesn't set DMA masks (since it doesn't use the DMA API),

SVA doesn't work through the VFIO framework.

so this appears to be relying on another driver having bound previously,

Yes. You are right.

otherwise the mask would still be the default 32-bit one from pci_setup_device(). I'm not sure that's an entirely robust assumption.

Currently SVA implementation always requires a native kernel driver. The
assumption is that the drivers should check and set 64-bit addressing
capability before calling iommu_sva_xxx() APIs.


+        return -ENODEV;
      if (intel_iommu_enable_pasid(iommu, dev))
          return -ENODEV;

Best regards,