[PATCH V1 net 2/4] net: ena: set initial DMA width to avoid intel iommu issue

[Shay Agroskin]

The ENA driver uses the readless mechanism, which uses DMA, to find
out what the DMA mask is supposed to be.

If DMA is used without setting the dma_mask first, it causes the
Intel IOMMU driver to think that ENA is a 32-bit device and therefore
disables IOMMU passthrough permanently.

This patch sets the dma_mask to be ENA_MAX_PHYS_ADDR_SIZE_BITS=48
before readless initialization in
ena_device_init()->ena_com_mmio_reg_read_request_init(),
which is large enough to workaround the intel_iommu issue.

DMA mask is set again to the correct value after it's received from the
device after readless is initialized.

Fixes: 1738cd3ed342 ("net: ena: Add a driver for Amazon Elastic Network 
Adapters (ENA)")
Signed-off-by: Mike Cui <mike...@amazon.com>
Signed-off-by: Arthur Kiyanovski <akiy...@amazon.com>
Signed-off-by: Shay Agroskin <shay...@amazon.com>
---
 drivers/net/ethernet/amazon/ena/ena_netdev.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/net/ethernet/amazon/ena/ena_netdev.c 
b/drivers/net/ethernet/amazon/ena/ena_netdev.c
index 574c2b5ba21e..854a22e692bf 100644
--- a/drivers/net/ethernet/amazon/ena/ena_netdev.c
+++ b/drivers/net/ethernet/amazon/ena/ena_netdev.c
@@ -4146,6 +4146,19 @@ static int ena_probe(struct pci_dev *pdev, const struct 
pci_device_id *ent)
                return rc;
        }
 
+       rc = pci_set_dma_mask(pdev, DMA_BIT_MASK(ENA_MAX_PHYS_ADDR_SIZE_BITS));
+       if (rc) {
+               dev_err(&pdev->dev, "pci_set_dma_mask failed %d\n", rc);
+               goto err_disable_device;
+       }
+
+       rc = pci_set_consistent_dma_mask(pdev, 
DMA_BIT_MASK(ENA_MAX_PHYS_ADDR_SIZE_BITS));
+       if (rc) {
+               dev_err(&pdev->dev, "err_pci_set_consistent_dma_mask failed 
%d\n",
+                       rc);
+               goto err_disable_device;
+       }
+
        pci_set_master(pdev);
 
        ena_dev = vzalloc(sizeof(*ena_dev));
-- 
2.17.1