0aaa68532e
Joey reports that booting 52-bit VA capable builds on 52-bit VA capable
CPUs is broken since commit 0d9b1ffefabe ("arm64: mm: make vabits_actual
a build time constant if possible"). This is due to the fact that the
primary CPU reads the vabits_actual variable before it has been
assigned.
The reason for deferring the assignment of vabits_actual was that we try
to perform as few stores to memory as we can with the MMU and caches
off, due to the cache coherency issues it creates.
Since __cpu_setup() [which is where the read of vabits_actual occurs] is
also called on the secondary boot path, we cannot just read the CPU ID
registers directly, given that the size of the VA space is decided by
the capabilities of the primary CPU. So let's read vabits_actual only on
the secondary boot path, and read the CPU ID registers directly on the
primary boot path, by making it a function parameter of __cpu_setup().
To ensure that all users of vabits_actual (including kasan_early_init())
observe the correct value, move the assignment of vabits_actual back
into asm code, but still defer it to after the MMU and caches have been
enabled.
Cc: Will Deacon <will@kernel.org>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Fixes: 0d9b1ffefabe ("arm64: mm: make vabits_actual a build time constant if possible")
Reported-by: Joey Gouly <joey.gouly@arm.com>
Co-developed-by: Joey Gouly <joey.gouly@arm.com>
Signed-off-by: Joey Gouly <joey.gouly@arm.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20220701111045.2944309-1-ardb@kernel.org
Signed-off-by: Will Deacon <will@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.