From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753252Ab1JALYF (ORCPT ); Sat, 1 Oct 2011 07:24:05 -0400 Received: from mtagate2.uk.ibm.com ([194.196.100.162]:34536 "EHLO mtagate2.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751375Ab1JALYA (ORCPT ); Sat, 1 Oct 2011 07:24:00 -0400 Subject: Re: [PATCH RFC 7/8] s390/jump-label: add arch_jump_label_transform_early() From: Jan Glauber To: Jeremy Fitzhardinge Cc: Steven Rostedt , "David S. Miller" , David Daney , Michael Ellerman , Jason Baron , the arch/x86 maintainers , Xen Devel , Linux Kernel Mailing List , Jeremy Fitzhardinge In-Reply-To: <4E85E867.8080809@goop.org> References: <1317394099.11297.54.camel@localhost.localdomain> <4E85E867.8080809@goop.org> Content-Type: text/plain; charset="windows-1251" Date: Sat, 01 Oct 2011 13:22:17 +0200 Message-Id: <1317468137.11297.70.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.24.5 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2011-09-30 at 09:03 -0700, Jeremy Fitzhardinge wrote: > On 09/30/2011 07:48 AM, Jan Glauber wrote: > > On Thu, 2011-09-29 at 16:26 -0700, Jeremy Fitzhardinge wrote: > >> From: Jeremy Fitzhardinge > >> > >> This allows jump-label entries to be modified early, in a pre-SMP > >> environment. > >> > >> Signed-off-by: Jeremy Fitzhardinge > >> Cc: Jan Glauber > > Hi Jeremy, > > > > Your patch looks fine, if you can fix the minor compiler warnings > > below. Excluding stop_machine() on pre-SMP also looks safer too me. > > Do you think there would be an actual problem, or are you just being > cautious? Just cautious since stop_machine() is quite a big hammer. Who knows how many jump labels we might get? So without an early exit in stop_machine() for pre-SMP we might waste performance there. > It seems to me - in general - stop_machine could just be defined to be a > no-op (ie, just directly calls the callback) until enough SMP is > initialized for it to make sense, rather than having to make every user > work around it (if there's a chance they might call it early). Agreed. > > CC arch/s390/kernel/jump_label.o > > arch/s390/kernel/jump_label.c: In function ‘__jump_label_transform’: > > arch/s390/kernel/jump_label.c:41:2: error: ‘rc’ undeclared (first use in this function) > > arch/s390/kernel/jump_label.c:41:2: note: each undeclared identifier is reported only once for each function it appears in > > arch/s390/kernel/jump_label.c:41:2: warning: passing argument 1 of ‘probe_kernel_write’ makes pointer from integer without a cast [enabled by default] > > include/linux/uaccess.h:108:21: note: expected ‘void *’ but argument is of type ‘jump_label_t’ > > arch/s390/kernel/jump_label.c:28:19: warning: unused variable ‘args’ [-Wunused-variable] > > make[2]: *** [arch/s390/kernel/jump_label.o] Error 1 > > > > > > Like so? Yes, that compiles! --Jan > From 9572689d1e5e6f54a1936a1dca09a6920d1bce27 Mon Sep 17 00:00:00 2001 > From: Jeremy Fitzhardinge > Date: Thu, 29 Sep 2011 10:58:46 -0700 > Subject: [PATCH] s390/jump-label: add arch_jump_label_transform_early() > > This allows jump-label entries to be modified early, in a pre-SMP > environment. > > Signed-off-by: Jeremy Fitzhardinge > Cc: Jan Glauber > > diff --git a/arch/s390/kernel/jump_label.c b/arch/s390/kernel/jump_label.c > index 44cc06b..4fbe63b 100644 > --- a/arch/s390/kernel/jump_label.c > +++ b/arch/s390/kernel/jump_label.c > @@ -18,26 +18,15 @@ struct insn { > } __packed; > > struct insn_args { > - unsigned long *target; > - struct insn *insn; > - ssize_t size; > + struct jump_entry *entry; > + enum jump_label_type type; > }; > > -static int __arch_jump_label_transform(void *data) > +static void __jump_label_transform(struct jump_entry *entry, > + enum jump_label_type type) > { > - struct insn_args *args = data; > - int rc; > - > - rc = probe_kernel_write(args->target, args->insn, args->size); > - WARN_ON_ONCE(rc < 0); > - return 0; > -} > - > -void arch_jump_label_transform(struct jump_entry *entry, > - enum jump_label_type type) > -{ > - struct insn_args args; > struct insn insn; > + int rc; > > if (type == JUMP_LABEL_ENABLE) { > /* brcl 15,offset */ > @@ -49,11 +38,33 @@ void arch_jump_label_transform(struct jump_entry *entry, > insn.offset = 0; > } > > - args.target = (void *) entry->code; > - args.insn = &insn; > - args.size = JUMP_LABEL_NOP_SIZE; > + rc = probe_kernel_write((void *)entry->code, &insn, JUMP_LABEL_NOP_SIZE); > + WARN_ON_ONCE(rc < 0); > +} > > - stop_machine(__arch_jump_label_transform, &args, NULL); > +static int __sm_arch_jump_label_transform(void *data) > +{ > + struct insn_args *args = data; > + > + __jump_label_transform(args->entry, args->type); > + return 0; > +} > + > +void arch_jump_label_transform(struct jump_entry *entry, > + enum jump_label_type type) > +{ > + struct insn_args args; > + > + args.entry = entry; > + args.type = type; > + > + stop_machine(__sm_arch_jump_label_transform, &args, NULL); > +} > + > +void __init arch_jump_label_transform_early(struct jump_entry *entry, > + enum jump_label_type type) > +{ > + __jump_label_transform(entry, type); > } > > #endif > > J >