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[ Upstream commite8dfdf3162] Unlike x86, which has machinery to deal with page faults that occur during the execution of EFI runtime services, arm64 has nothing like that, and a synchronous exception raised by firmware code brings down the whole system. With more EFI based systems appearing that were not built to run Linux (such as the Windows-on-ARM laptops based on Qualcomm SOCs), as well as the introduction of PRM (platform specific firmware routines that are callable just like EFI runtime services), we are more likely to run into issues of this sort, and it is much more likely that we can identify and work around such issues if they don't bring down the system entirely. Since we already use a EFI runtime services call wrapper in assembler, we can quite easily add some code that captures the execution state at the point where the call is made, allowing us to revert to this state and proceed execution if the call triggered a synchronous exception. Given that the kernel and the firmware don't share any data structures that could end up in an indeterminate state, we can happily continue running, as long as we mark the EFI runtime services as unavailable from that point on. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Acked-by: Catalin Marinas <catalin.marinas@arm.com> Stable-dep-of:8a9a1a1873("arm64: efi: Avoid workqueue to check whether EFI runtime is live") Signed-off-by: Sasha Levin <sashal@kernel.org>
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.