Ubuntu
linux package

  1. Bionic (18.04)
  2. Bug #1771467
  3. Comment #32

Comment 32 for bug 1771467

Revision history for this message
In , okaya (okaya-linux-kernel-bugs) wrote :

I think the motivation is for rogue transactions from the devices not to hit the system memory while a new kernel is booted via kexec.

It is not an issue when IOMMU is not present since the second kernel that is booting doesn't share the same address space.

However; when IOMMU is present, an adapter can corrupt the newly booting kernel. So, you ideally want to have bus master bit cleared for a clean boot.

What is interesting is that kexec is already doing this job in pci_device_shutdown(). This extra clear is unnecessary. I'll post a patch to remove it.