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Volodymyr reports that using a Xen DomU as a nested guest (where
HCR_EL2.E2H == 0), ATS12 results in a translation that stops at
the L2's S1, which isn't something you'd normally expects.
Comparing the code against the spec proves to be illuminating,
and suggests that the author of such code must have been tired,
cross-eyed, drunk, or maybe all of the above.
The gist of it is that, apart from HCR_EL2.VM or HCR_EL2.DC being
0, only the use of the EL2&0 translation regime limits the walk
to S1 only, and that we must finish the S2 walk in any other case.
Which solves the above issue, as E2H==0 indicates that ATS12 walks
the EL1&0 translation regime.
Explicitly checking for EL2&0 fixes this.
Reported-by: Volodymyr Babchuk <volodymyr_babchuk@epam.com>
Suggested-by: Oliver Upton <oliver.upton@linux.dev>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Fixes: be04cebf3e ("KVM: arm64: nv: Add emulation of AT S12E{0,1}{R,W}")
Link: https://lore.kernel.org/r/20250806141707.3479194-2-volodymyr_babchuk@epam.com
Link: https://lore.kernel.org/r/20250809144811.2314038-2-maz@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
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 reStructuredText 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.