Since commit 08a27c1c3ecf ("iommu: Add support to change default domain
of an iommu group") a user can switch a device between IOMMU and direct
DMA through sysfs. This doesn't work for AMD IOMMU at the moment because
dev->dma_ops is not cleared when switching from a DMA to an identity
IOMMU domain. The DMA layer thus attempts to use the dma-iommu ops on an
identity domain, causing an oops:
# echo 0000:00:05.0 > /sys/sys/bus/pci/drivers/e1000e/unbind
# echo identity > /sys/bus/pci/devices/0000:00:05.0/iommu_group/type
# echo 0000:00:05.0 > /sys/sys/bus/pci/drivers/e1000e/bind
...
[ 190.017587] BUG: kernel NULL pointer dereference, address: 0000000000000028
...
[ 190.027375] Call Trace:
[ 190.027561] iommu_dma_alloc+0xd0/0x100
[ 190.027840] e1000e_setup_tx_resources+0x56/0x90
[ 190.028173] e1000e_open+0x75/0x5b0
Implement arch_teardown_dma_ops() on x86 to clear the device's dma_ops
pointer during driver unbind.
Fixes: 08a27c1c3ecf ("iommu: Add support to change default domain of an iommu
group")
Signed-off-by: Jean-Philippe Brucker <jean-phili...@linaro.org>
---
arch/x86/Kconfig | 1 +
arch/x86/kernel/pci-dma.c | 7 +++++++
2 files changed, 8 insertions(+)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 2792879d398e..2c90f8de3e20 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -85,6 +85,7 @@ config X86
select ARCH_HAS_STRICT_MODULE_RWX
select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
select ARCH_HAS_SYSCALL_WRAPPER
+ select ARCH_HAS_TEARDOWN_DMA_OPS if IOMMU_DMA
select ARCH_HAS_UBSAN_SANITIZE_ALL
select ARCH_HAS_DEBUG_WX
select ARCH_HAVE_NMI_SAFE_CMPXCHG
diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
index de234e7a8962..60a4ec22d849 100644
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -154,3 +154,10 @@ static void via_no_dac(struct pci_dev *dev)
DECLARE_PCI_FIXUP_CLASS_FINAL(PCI_VENDOR_ID_VIA, PCI_ANY_ID,
PCI_CLASS_BRIDGE_PCI, 8, via_no_dac);
#endif
+
+#ifdef CONFIG_ARCH_HAS_TEARDOWN_DMA_OPS
+void arch_teardown_dma_ops(struct device *dev)
+{
+ set_dma_ops(dev, NULL);
+}
+#endif
--
2.31.1
