From f233f7f1581e78fd9b4023f2e7d8c1ed89020cc9 Mon Sep 17 00:00:00 2001 From: "Peter Zijlstra (Intel)" Date: Fri, 24 Apr 2015 14:56:38 -0400 Subject: locking/pvqspinlock, x86: Implement the paravirt qspinlock call patching We use the regular paravirt call patching to switch between: native_queued_spin_lock_slowpath() __pv_queued_spin_lock_slowpath() native_queued_spin_unlock() __pv_queued_spin_unlock() We use a callee saved call for the unlock function which reduces the i-cache footprint and allows 'inlining' of SPIN_UNLOCK functions again. We further optimize the unlock path by patching the direct call with a "movb $0,%arg1" if we are indeed using the native unlock code. This makes the unlock code almost as fast as the !PARAVIRT case. This significantly lowers the overhead of having CONFIG_PARAVIRT_SPINLOCKS enabled, even for native code. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Waiman Long Signed-off-by: Peter Zijlstra (Intel) Cc: Andrew Morton Cc: Boris Ostrovsky Cc: Borislav Petkov Cc: Daniel J Blueman Cc: David Vrabel Cc: Douglas Hatch Cc: H. Peter Anvin Cc: Konrad Rzeszutek Wilk Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Paolo Bonzini Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Raghavendra K T Cc: Rik van Riel Cc: Scott J Norton Cc: Thomas Gleixner Cc: virtualization@lists.linux-foundation.org Cc: xen-devel@lists.xenproject.org Link: http://lkml.kernel.org/r/1429901803-29771-10-git-send-email-Waiman.Long@hp.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/paravirt_patch_32.c | 22 ++++++++++++++++++---- 1 file changed, 18 insertions(+), 4 deletions(-) (limited to 'arch/x86/kernel/paravirt_patch_32.c') diff --git a/arch/x86/kernel/paravirt_patch_32.c b/arch/x86/kernel/paravirt_patch_32.c index d9f32e6d6ab6..e1b013696dde 100644 --- a/arch/x86/kernel/paravirt_patch_32.c +++ b/arch/x86/kernel/paravirt_patch_32.c @@ -12,6 +12,10 @@ DEF_NATIVE(pv_mmu_ops, read_cr3, "mov %cr3, %eax"); DEF_NATIVE(pv_cpu_ops, clts, "clts"); DEF_NATIVE(pv_cpu_ops, read_tsc, "rdtsc"); +#if defined(CONFIG_PARAVIRT_SPINLOCKS) && defined(CONFIG_QUEUED_SPINLOCKS) +DEF_NATIVE(pv_lock_ops, queued_spin_unlock, "movb $0, (%eax)"); +#endif + unsigned paravirt_patch_ident_32(void *insnbuf, unsigned len) { /* arg in %eax, return in %eax */ @@ -24,6 +28,8 @@ unsigned paravirt_patch_ident_64(void *insnbuf, unsigned len) return 0; } +extern bool pv_is_native_spin_unlock(void); + unsigned native_patch(u8 type, u16 clobbers, void *ibuf, unsigned long addr, unsigned len) { @@ -47,14 +53,22 @@ unsigned native_patch(u8 type, u16 clobbers, void *ibuf, PATCH_SITE(pv_mmu_ops, write_cr3); PATCH_SITE(pv_cpu_ops, clts); PATCH_SITE(pv_cpu_ops, read_tsc); - - patch_site: - ret = paravirt_patch_insns(ibuf, len, start, end); - break; +#if defined(CONFIG_PARAVIRT_SPINLOCKS) && defined(CONFIG_QUEUED_SPINLOCKS) + case PARAVIRT_PATCH(pv_lock_ops.queued_spin_unlock): + if (pv_is_native_spin_unlock()) { + start = start_pv_lock_ops_queued_spin_unlock; + end = end_pv_lock_ops_queued_spin_unlock; + goto patch_site; + } +#endif default: ret = paravirt_patch_default(type, clobbers, ibuf, addr, len); break; + +patch_site: + ret = paravirt_patch_insns(ibuf, len, start, end); + break; } #undef PATCH_SITE return ret; -- cgit v1.2.3