[PATCH v6 0/5] Add a unified parameter "nopvspin"

From: Zhenzhong Duan
Date: Mon Oct 14 2019 - 21:21:36 EST

There are cases folks want to disable spinlock optimization for
debug/test purpose. Xen and hyperv already have parameters "xen_nopvspin"
and "hv_nopvspin" to support that, but kvm doesn't.

The first patch adds that feature to KVM guest with "nopvspin".

For compatibility reason original parameters "xen_nopvspin" and
"hv_nopvspin" are retained and marked obsolete.

PATCH1: add Reviewed-by [Vitaly Kuznetsov]
PATCH2: change 'pv' to 'PV', add Reviewed-by [Vitaly Kuznetsov]
PATCH3: refactor 'if' branch in kvm_spinlock_init() [Vitaly Kuznetsov]

PATCH1: new patch to revert a currently unnecessory commit,
code is simpler a bit after that change. [Boris Ostrovsky]
PATCH3: fold 'if' statement,add comments on virt_spin_lock_key,
reorder with PATCH2 to better reflect dependency
PATCH4: fold 'if' statement, add Reviewed-by [Boris Ostrovsky]
PATCH5: add Reviewed-by [Michael Kelley]

PATCH1: use variable name nopvspin instead of pvspin and
defined it as __initdata, changed print message,
updated patch description [Sean Christopherson]
PATCH2: remove Suggested-by, use "kvm-guest:" prefix [Sean Christopherson]
PATCH3: make variable nopvsin and xen_pvspin coexist
remove Reviewed-by due to code change [Sean Christopherson]
PATCH4: make variable nopvsin and hv_pvspin coexist [Sean Christopherson]

PATCH2: Fix indentation

PATCH1: pick the print code change into separate PATCH2,
updated patch description [Vitaly Kuznetsov]
PATCH2: new patch with print code change [Vitaly Kuznetsov]
PATCH3: add Reviewed-by [Juergen Gross]

Zhenzhong Duan (5):
Revert "KVM: X86: Fix setup the virt_spin_lock_key before static key
get initialized"
x86/kvm: Change print code to use pr_*() format
x86/kvm: Add "nopvspin" parameter to disable PV spinlocks
xen: Mark "xen_nopvspin" parameter obsolete
x86/hyperv: Mark "hv_nopvspin" parameter obsolete

Documentation/admin-guide/kernel-parameters.txt | 14 ++++-
arch/x86/hyperv/hv_spinlock.c | 4 ++
arch/x86/include/asm/qspinlock.h | 1 +
arch/x86/kernel/kvm.c | 76 ++++++++++++++++---------
arch/x86/xen/spinlock.c | 4 +-
kernel/locking/qspinlock.c | 7 +++
6 files changed, 75 insertions(+), 31 deletions(-)