From: Andrew Cooper Date: Wed, 14 Mar 2018 15:20:05 +0000 (+0000) Subject: x86/pv: Avoid locked bit manipulation in register_guest_callback() X-Git-Tag: archive/raspbian/4.14.0+80-gd101b417b7-1+rpi1^2~63^2~3599 X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=ad43ce53ad2dab6673e750f8793560e6e460ae28;p=xen.git x86/pv: Avoid locked bit manipulation in register_guest_callback() Changes to arch.vgc_flags are made to current in syncrhonous context only, and don't need to be locked. (The only other changes are via arch_set_info_guest(), which operates on descheduled vcpus only). Replace the {set,clear}_bit() calls with compiler-visible bitwise operations. Signed-off-by: Andrew Cooper Reviewed-by: Jan Beulich Reviewed-by: Roger Pau Monné --- diff --git a/xen/arch/x86/pv/callback.c b/xen/arch/x86/pv/callback.c index 2550a726d2..394726a197 100644 --- a/xen/arch/x86/pv/callback.c +++ b/xen/arch/x86/pv/callback.c @@ -82,21 +82,17 @@ static long register_guest_callback(struct callback_register *reg) case CALLBACKTYPE_failsafe: curr->arch.pv_vcpu.failsafe_callback_eip = reg->address; if ( reg->flags & CALLBACKF_mask_events ) - set_bit(_VGCF_failsafe_disables_events, - &curr->arch.vgc_flags); + curr->arch.vgc_flags |= VGCF_failsafe_disables_events; else - clear_bit(_VGCF_failsafe_disables_events, - &curr->arch.vgc_flags); + curr->arch.vgc_flags &= ~VGCF_failsafe_disables_events; break; case CALLBACKTYPE_syscall: curr->arch.pv_vcpu.syscall_callback_eip = reg->address; if ( reg->flags & CALLBACKF_mask_events ) - set_bit(_VGCF_syscall_disables_events, - &curr->arch.vgc_flags); + curr->arch.vgc_flags |= VGCF_syscall_disables_events; else - clear_bit(_VGCF_syscall_disables_events, - &curr->arch.vgc_flags); + curr->arch.vgc_flags &= ~VGCF_syscall_disables_events; break; case CALLBACKTYPE_syscall32: @@ -230,11 +226,9 @@ static long compat_register_guest_callback(struct compat_callback_register *reg) curr->arch.pv_vcpu.failsafe_callback_cs = reg->address.cs; curr->arch.pv_vcpu.failsafe_callback_eip = reg->address.eip; if ( reg->flags & CALLBACKF_mask_events ) - set_bit(_VGCF_failsafe_disables_events, - &curr->arch.vgc_flags); + curr->arch.vgc_flags |= VGCF_failsafe_disables_events; else - clear_bit(_VGCF_failsafe_disables_events, - &curr->arch.vgc_flags); + curr->arch.vgc_flags &= ~VGCF_failsafe_disables_events; break; case CALLBACKTYPE_syscall32: