powerpc: add running_clock for powerpc to prevent spurious softlockup warnings

On POWER8 virtualised kernels the VTB register can be read to have a view
of time that only increases while the guest is running.  This will prevent
guests from seeing time jump if a guest is paused for significant amounts
of time.

On POWER7 and below virtualised kernels stolen time is subtracted from
local_clock as a best effort approximation.  This will not eliminate
spurious warnings in the case of a suspended guest but may reduce the
occurance in the case of softlockups due to host over commit.

Bare metal kernels should avoid reading the VTB as KVM does not restore
sane values when not executing, the approxmation is fine as host kernels
won't observe any stolen time.

[[email protected]: coding-style fixes]
Signed-off-by: Cyril Bur <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Andrew Jones <[email protected]>
Acked-by: Don Zickus <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Ulrich Obergfell <[email protected]>
Cc: chai wen <[email protected]>
Cc: Fabian Frederick <[email protected]>
Cc: Aaron Tomlin <[email protected]>
Cc: Ben Zhang <[email protected]>
Cc: Martin Schwidefsky <[email protected]>
Cc: John Stultz <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions