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When saving the floating point context in fpsimd_save() we always reference the state using last-> rather than using current->. Looking at the FP code in isolation the reason for this is not entirely obvious, it's done because when KVM is running it will bind the guest context and rely on the host writing out the guest state on context switch away from the guest. There's a slight trick here in that KVM still uses TIF_FOREIGN_FPSTATE and TIF_SVE to communicate what needs to be saved, it maintains those flags and restores them when it is done running the guest so that the normal restore paths function when we return back to userspace. Add a comment to explain this to help future readers work out what's going on a bit faster. Signed-off-by: Mark Brown <broonie@kernel.org> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Marc Zyngier <maz@kernel.org> Link: https://lore.kernel.org/r/20220124161115.115200-1-broonie@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.