Il 25/04/2014 17:19, James Hogan ha scritto:
Expose the KVM guest CP0_Count bias (from the monotonic kernel time) to
userland in nanosecond units via a new KVM_REG_MIPS_COUNT_BIAS register
accessible with the KVM_{GET,SET}_ONE_REG ioctls. This gives userland
control of the bias so that it can exactly match its own monotonic time.
The nanosecond bias is stored separately from the raw bias used
internally (since nanoseconds isn't a convenient or efficient unit for
various timer calculations), and is recalculated each time the raw count
bias is altered. The raw count bias used in CP0_Count determination is
recalculated when the nanosecond bias is altered via the KVM_SET_ONE_REG
ioctl.
Signed-off-by: James Hogan <james.hogan@xxxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Gleb Natapov <gleb@xxxxxxxxxx>
Cc: kvm@xxxxxxxxxxxxxxx
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Cc: linux-mips@xxxxxxxxxxxxxx
Cc: David Daney <david.daney@xxxxxxxxxx>
Cc: Sanjay Lal <sanjayl@xxxxxxxxxxx>
If it is possible and not too hairy to use a raw value in userspace
(together with KVM_REG_MIPS_COUNT_HZ), please do it---my suggestions
were just that, a suggestion. Otherwise, the patch looks good.
Paolo
