On 09/02/18 17:54, Suzuki K Poulose wrote:
This series reworks the arm64 CPU capabilities handling (which
manages the system features and errata). The current infrastructure
doesn't allow fine control for handling different features or errata.
There is one rule for features and another rule for errata.
* Features are checked only once, after all the boot time CPUs are
activated. Any new CPU that is brought up is prevented from booting
if it misses a feature already established. If the new CPU has a
feature not enabled already, it is allowed to boot.
* Errata checks are performed on all the CPUs and any new CPU is
OK to miss the capability. However if a late CPU requires a work around,
then we fail the CPU.
This doesn't always apply to some features. e.g, KPTI is a security
feature which should be applied when at least one CPU needs it. So,
the tests should be performed on all the booting CPUs individually.
Also, if a CPU that needs this security feature is brought up later,
when the system has not enabled it, the CPU can boot making the system
insecure. Another exception is the hardware DBM for page tables. The
kernel can safely run with a mix of CPUs that have the feature turned
on and off. This again causes problem when a new CPU is brought up
which may not have the feature, which is killed.
Also there are other features like, GICV3 system register access,
which now need to be enabled very early based on the boot CPU to
allow the use of Priority handling to implement NMI.
This calls for finer level of control per capability and the series
implements the same by defining how to deal with a conflict of a
given capability on a CPU with that of the system level state. It
also consolidates the handling of features and errata into generic
helpers. The table of features and errata are left as they are to
allow easier look up for a given type.
The series also gets rid of duplicate entries for a single capability
by introducing a wrapper entry which takes care of managing a list
of entries with distinct matches/enable pair.
We also cleans up the MIDR range handling and cleans up some of the
errata checks where the entries were duplicated for checking different
CPU models. Finally it also implements a work around for Arm Cortex-A55
erratum 1024718 based on the new infrastructure.
Applies on arm64 for-next/core. The tree is available at :
Apologies for the mess... obviously I messed up my folder.
If anyone needs the patches for testing, the branch above is sane.