7f632d331d
For ARM64_WORKAROUND_2658417, we use a cpu_enable() callback to hide the ID_AA64ISAR1_EL1.BF16 ID register field. This is a little awkward as CPUs may attempt to apply the workaround concurrently, requiring that we protect the bulk of the callback with a raw_spinlock, and requiring some pointless work every time a CPU is subsequently hotplugged in. This patch makes this a little simpler by handling the masking once at boot time. A new user_feature_fixup() function is called at the start of setup_user_features() to mask the feature, matching the style of elf_hwcap_fixup(). The ARM64_WORKAROUND_2658417 cpucap is added to cpucap_is_possible() so that code can be elided entirely when this is not possible. Note that the ARM64_WORKAROUND_2658417 capability is matched with ERRATA_MIDR_RANGE(), which implicitly gives the capability a ARM64_CPUCAP_LOCAL_CPU_ERRATUM type, which forbids the late onlining of a CPU with the erratum if the erratum was not present at boot time. Therefore this patch doesn't change the behaviour for late onlining. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Cc: James Morse <james.morse@arm.com> Cc: Mark Brown <broonie@kernel.org> Cc: Suzuki K Poulose <suzuki.poulose@arm.com> Cc: Will Deacon <will@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.