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428c491332
Currently ENA only provides the PCI remove() handler, used during rmmod for example. This is not called on shutdown/kexec path; we are potentially creating a failure scenario on kexec: (a) Kexec is triggered, no shutdown() / remove() handler is called for ENA; instead pci_device_shutdown() clears the master bit of the PCI device, stopping all DMA transactions; (b) Kexec reboot happens and the device gets enabled again, likely having its FW with that DMA transaction buffered; then it may trigger the (now invalid) memory operation in the new kernel, corrupting kernel memory area. This patch aims to prevent this, by implementing a shutdown() handler quite similar to the remove() one - the difference being the handling of the netdev, which is unregistered on remove(), but following the convention observed in other drivers, it's only detached on shutdown(). This prevents an odd issue in AWS Nitro instances, in which after the 2nd kexec the next one will fail with an initrd corruption, caused by a wild DMA write to invalid kernel memory. The lspci output for the adapter present in my instance is: 00:05.0 Ethernet controller [0200]: Amazon.com, Inc. Elastic Network Adapter (ENA) [1d0f:ec20] Suggested-by: Gavin Shan <gshan@redhat.com> Signed-off-by: Guilherme G. Piccoli <gpiccoli@canonical.com> Acked-by: Sameeh Jubran <sameehj@amazon.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.