From 9043442b43b1fddf202591b84702863286700c1a Mon Sep 17 00:00:00 2001 From: Juergen Gross Date: Wed, 6 Sep 2017 19:36:24 +0200 Subject: locking/paravirt: Use new static key for controlling call of virt_spin_lock() There are cases where a guest tries to switch spinlocks to bare metal behavior (e.g. by setting "xen_nopvspin" boot parameter). Today this has the downside of falling back to unfair test and set scheme for qspinlocks due to virt_spin_lock() detecting the virtualized environment. Add a static key controlling whether virt_spin_lock() should be called or not. When running on bare metal set the new key to false. Signed-off-by: Juergen Gross Signed-off-by: Peter Zijlstra (Intel) Acked-by: Waiman Long Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: akataria@vmware.com Cc: boris.ostrovsky@oracle.com Cc: chrisw@sous-sol.org Cc: hpa@zytor.com Cc: jeremy@goop.org Cc: rusty@rustcorp.com.au Cc: virtualization@lists.linux-foundation.org Cc: xen-devel@lists.xenproject.org Link: http://lkml.kernel.org/r/20170906173625.18158-2-jgross@suse.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/paravirt.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) (limited to 'arch/x86/kernel/paravirt.c') diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c index 19a3e8f..041096b 100644 --- a/arch/x86/kernel/paravirt.c +++ b/arch/x86/kernel/paravirt.c @@ -115,8 +115,18 @@ unsigned paravirt_patch_jmp(void *insnbuf, const void *target, return 5; } -/* Neat trick to map patch type back to the call within the - * corresponding structure. */ +DEFINE_STATIC_KEY_TRUE(virt_spin_lock_key); + +void __init native_pv_lock_init(void) +{ + if (!static_cpu_has(X86_FEATURE_HYPERVISOR)) + static_branch_disable(&virt_spin_lock_key); +} + +/* + * Neat trick to map patch type back to the call within the + * corresponding structure. + */ static void *get_call_destination(u8 type) { struct paravirt_patch_template tmpl = { -- cgit v1.1