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4be518d838
Most platforms allocate IOMMU table structures (specifically it_map) at the boot time and when this fails - it is a valid reason for panic(). However the powernv platform allocates it_map after a device is returned to the host OS after being passed through and this happens long after the host OS booted. It is quite possible to trigger the it_map allocation panic() and kill the host even though it is not necessary - the host OS can still use the DMA bypass mode (requires a tiny fraction of it_map's memory) and even if that fails, the host OS is runnnable as it was without the device for which allocating it_map causes the panic. Instead of immediately crashing in a powernv/ioda2 system, this prints an error and continues. All other platforms still call panic(). Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> Reviewed-by: David Gibson <david@gibson.dropbear.id.au> Reviewed-by: Leonardo Bras <leobras.c@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20210216033307.69863-3-aik@ozlabs.ru
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.