[PATCH 0/2] x86/vdso: Add Hyper-V TSC page clocksource support

From: Vitaly Kuznetsov
Date: Thu Feb 09 2017 - 09:11:06 EST


Hyper-V TSC page clocksource is suitable for vDSO, however, the protocol
defined by the hypervisor is different from VCLOCK_PVCLOCK. Implemented the
required support. Simple sysbench test shows the following results:

# time sysbench --test=memory --max-requests=500000 run
real 1m22.618s
user 0m50.193s
sys 0m32.268s

# time sysbench --test=memory --max-requests=500000 run
real 0m47.241s
user 0m47.117s
sys 0m0.008s

So it seems it is worth it. As nobody seems to be strongly offended by my RFC
I'm sending first non-RFC version. Patch 1 is made on top of K. Y.'s code
refactoring which moved tsc page clocksource to arch/x86/hyperv/hv_init.c,
this is currently present in Greg's char-misc-next tree.

Changes since RFC:
- Use mul_u64_u64_shr() instead of an open coded implementation
[Andy Lutomirski, Thomas Gleixner]
- Don't use the same pvclock_page for both VCLOCK_PVCLOCK and
VCLOCK_HVCLOCK, create another one [Andy Lutomirski]
- Fix issues reported by kbuild test robot.
- Rename HYPERV_CLOCK -> HYPERV_TSCPAGE to avoid the ambiguity.

I'm also going to try to optimize mul_u64_u64_shr() for 32bit but this can
be split from this series I guess.

Vitaly Kuznetsov (2):
hyperv: implement hv_get_tsc_page()
x86/vdso: Add VCLOCK_HVCLOCK vDSO clock read method

arch/x86/entry/vdso/vclock_gettime.c | 36 +++++++++++++++++++++++++++++++++++
arch/x86/entry/vdso/vdso-layout.lds.S | 3 ++-
arch/x86/entry/vdso/vdso2c.c | 3 +++
arch/x86/entry/vdso/vma.c | 7 +++++++
arch/x86/hyperv/hv_init.c | 12 ++++++++++--
arch/x86/include/asm/clocksource.h | 3 ++-
arch/x86/include/asm/mshyperv.h | 8 ++++++++
arch/x86/include/asm/vdso.h | 1 +
drivers/hv/Kconfig | 3 +++
9 files changed, 72 insertions(+), 4 deletions(-)