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KVM in nVHE mode divides up its VA space into two equal halves, and picks the half that does not conflict with the HYP ID map to map its linear region. This worked fine when the kernel's linear map itself was guaranteed to cover precisely as many bits of VA space, but this was changed by commitf4693c2716("arm64: mm: extend linear region for 52-bit VA configurations"). The result is that, depending on the placement of the ID map, kernel-VA to hyp-VA translations may produce addresses that either conflict with other HYP mappings (including the ID map itself) or generate addresses outside of the 52-bit addressable range, neither of which is likely to lead to anything useful. Given that 52-bit capable cores are guaranteed to implement VHE, this only affects configurations such as pKVM where we opt into non-VHE mode even if the hardware is VHE capable. So just for these configurations, let's limit the kernel linear map to 51 bits and work around the problem. Fixes:f4693c2716("arm64: mm: extend linear region for 52-bit VA configurations") Signed-off-by: Ard Biesheuvel <ardb@kernel.org> Link: https://lore.kernel.org/r/20210826165613.60774-1-ardb@kernel.org Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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.