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

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Date:   Wed, 18 Nov 2020 23:59:45 +0200
From:   Shay Agroskin <shayagr@...zon.com>
To:     <kuba@...nel.org>, <netdev@...r.kernel.org>
CC:     Shay Agroskin <shayagr@...zon.com>, <dwmw@...zon.com>,
        <zorik@...zon.com>, <matua@...zon.com>, <saeedb@...zon.com>,
        <msw@...zon.com>, <aliguori@...zon.com>, <nafea@...zon.com>,
        <gtzalik@...zon.com>, <netanel@...zon.com>, <alisaidi@...zon.com>,
        <benh@...zon.com>, <akiyano@...zon.com>, <sameehj@...zon.com>,
        <ndagan@...zon.com>, Mike Cui <mikecui@...zon.com>
Subject: [PATCH V1 net 2/4] net: ena: set initial DMA width to avoid intel iommu issue

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 <mikecui@...zon.com>
Signed-off-by: Arthur Kiyanovski <akiyano@...zon.com>
Signed-off-by: Shay Agroskin <shayagr@...zon.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