The D_NEEDMINOR flag was introduced for drivers that do not actually
depend on storing a device unit/minor number, but require the ability to
address the cdevs by this number, which is used by clone_create().
The cpuctl(4) driver sets D_NEEDMINOR, even though it doesn't use the
clone_create() API. Remove the flag, because maybe we want to get rid of
it somewhere in the far future.
features of CPUs like reading/writing machine-specific registers,
retrieving cpuid data, and updating microcode.
- Add cpucontrol(8) utility, that provides userland access to
the features of cpuctl(4).
- Add subsequent manpages.
The cpuctl(4) device operates as follows. The pseudo-device node cpuctlX
is created for each cpu present in the systems. The pseudo-device minor
number corresponds to the cpu number in the system. The cpuctl(4) pseudo-
device allows a number of ioctl to be preformed, namely RDMSR/WRMSR/CPUID
and UPDATE. The first pair alows the caller to read/write machine-specific
registers from the correspondent CPU. cpuid data could be retrieved using
the CPUID call, and microcode updates are applied via UPDATE.
The permissions are inforced based on the pseudo-device file permissions.
RDMSR/CPUID will be allowed when the caller has read access to the device
node, while WRMSR/UPDATE will be granted only when the node is opened
for writing. There're also a number of priv(9) checks.
The cpucontrol(8) utility is intened to provide userland access to
the cpuctl(4) device features. The utility also allows one to apply
cpu microcode updates.
Currently only Intel and AMD cpus are supported and were tested.
Approved by: kib
Reviewed by: rpaulo, cokane, Peter Jeremy
MFC after: 1 month
