From fc6ad5eadcd1694d2f1ee2717c8024efd8152e20 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Tue, 4 Aug 2026 07:15:41 +0000 Subject: x86/paravirt: Use static_call() for the paravirt spinlock ops queued_spin_lock_slowpath() and queued_spin_unlock() are dispatched through pv_ops_lock via the paravirt-ops ALTERNATIVE machinery, which picks the target (native inline store / hypervisor call) once at boot and cannot change at runtime. Convert both to static_call(). The site becomes a direct call patched in place (one byte smaller), and on native the unlock still collapses to the inline "movb $0, (%rdi)" store, so the fast path is unchanged. Unlike the ALTERNATIVE mechanism, a static_call() target can also be updated at runtime via static_call_update(). This is a prerequisite for the contended_release tracepoint, which has to swap in a traced unlock while the system is running. [ ilvokhin: commit message; fix PARAVIRT_SPINLOCKS=n build; teach __static_call_validate() about the inline unlock insn; make the slowpath site module-safe: static_call_mod() + EXPORT_STATIC_CALL_TRAMP(); pass @lock to the callee-save unlock, fixing a boot hang under CALL_DEPTH_TRACKING. Boot tested native + KVM PV guest. ] Signed-off-by: Peter Zijlstra (Intel) Co-developed-by: Dmitry Ilvokhin Signed-off-by: Dmitry Ilvokhin Signed-off-by: Peter Zijlstra (Intel) Acked-by: Juergen Gross Link: https://lore.kernel.org/all/20260603120811.GW3493090@noisy.programming.kicks-ass.net/ Link: https://patch.msgid.link/9a32ae399eb804a02a31af04dcabe7e7ee4f3fdf.1785778551.git.d@ilvokhin.com --- tools/arch/x86/include/asm/cpufeatures.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'tools') diff --git a/tools/arch/x86/include/asm/cpufeatures.h b/tools/arch/x86/include/asm/cpufeatures.h index 86d17b195e79..425452f8c375 100644 --- a/tools/arch/x86/include/asm/cpufeatures.h +++ b/tools/arch/x86/include/asm/cpufeatures.h @@ -225,7 +225,7 @@ #define X86_FEATURE_EPT_AD ( 8*32+17) /* "ept_ad" Intel Extended Page Table access-dirty bit */ #define X86_FEATURE_VMCALL ( 8*32+18) /* Hypervisor supports the VMCALL instruction */ #define X86_FEATURE_VMW_VMMCALL ( 8*32+19) /* VMware prefers VMMCALL hypercall instruction */ -#define X86_FEATURE_PVUNLOCK ( 8*32+20) /* PV unlock function */ +// free: was #define X86_FEATURE_PVUNLOCK ( 8*32+20) /* PV unlock function */ #define X86_FEATURE_VCPUPREEMPT ( 8*32+21) /* PV vcpu_is_preempted function */ #define X86_FEATURE_TDX_GUEST ( 8*32+22) /* "tdx_guest" Intel Trust Domain Extensions Guest */ -- cgit v1.2.3