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* [PATCH] x86/dma: Tear down DMA ops on driver unbind
@ 2021-04-14  8:26 Jean-Philippe Brucker
  2021-04-15  9:00 ` [tip: x86/urgent] " tip-bot2 for Jean-Philippe Brucker
  0 siblings, 1 reply; 4+ messages in thread
From: Jean-Philippe Brucker @ 2021-04-14  8:26 UTC (permalink / raw)
  To: tglx, mingo, bp, x86
  Cc: hpa, linux-kernel, joro, will, iommu, robin.murphy, hch,
	Jean-Philippe Brucker

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-philippe@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


^ permalink raw reply	[flat|nested] 4+ messages in thread

end of thread, other threads:[~2021-04-19  8:59 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2021-04-14  8:26 [PATCH] x86/dma: Tear down DMA ops on driver unbind Jean-Philippe Brucker
2021-04-15  9:00 ` [tip: x86/urgent] " tip-bot2 for Jean-Philippe Brucker
2021-04-17 12:06   ` Borislav Petkov
2021-04-19  8:59     ` Jean-Philippe Brucker

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