From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752286Ab0DZOfV (ORCPT ); Mon, 26 Apr 2010 10:35:21 -0400 Received: from ey-out-2122.google.com ([74.125.78.26]:42773 "EHLO ey-out-2122.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751128Ab0DZOfS convert rfc822-to-8bit (ORCPT ); Mon, 26 Apr 2010 10:35:18 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type :content-transfer-encoding; b=g4nYo7ijCG7y2keMYHks0gFCgyzdgwlEsfFe9U5AAo2rzsCxxCv2YeqLgk20INlyGh R9gavCDc0gm04OUN5wPagwaN6Tq4QroUmDecxbaxKwNfY4j/t7EjnrFhAh+Jlhn7pKms wwEC9CNZlhnaikX/24iThLYJ1Jr30cx1cPRVs= MIME-Version: 1.0 In-Reply-To: <20100426140535.GA17135@ericsson.com> References: <1271780217-27472-1-git-send-email-guenter.roeck@ericsson.com> <4BD55E85.4020709@cs.helsinki.fi> <20100426140535.GA17135@ericsson.com> Date: Mon, 26 Apr 2010 17:35:16 +0300 X-Google-Sender-Auth: da64cf50bdb7cce0 Message-ID: Subject: Re: [PATCH v3] x86: Do not write into VGA memory space if there is no VGA device in the system From: Pekka Enberg To: Guenter Roeck Cc: "linux-kernel@vger.kernel.org" , "mingo@redhat.com" , "x86@kernel.org" , "H. Peter Anvin" Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 26, 2010 at 5:05 PM, Guenter Roeck wrote: > On Mon, Apr 26, 2010 at 05:36:05AM -0400, Pekka Enberg wrote: >> Guenter Roeck kirjoitti: >> > Ensure that early_printk() does not write into VGA memory space >> > if there is not VGA device in the system. >> > >> > Signed-off-by: Guenter Roeck >> > --- >> > v3: >> > Changes are now limited to early_printk.c. Functionality is retained, meaning >> > there will still be output on the VGA console before setup_early_printk() >> > is called, but only if a VGA device is known to exist in the system. >> > >> >  arch/x86/kernel/early_printk.c |   17 +++++++++++++---- >> >  1 files changed, 13 insertions(+), 4 deletions(-) >> > >> > diff --git a/arch/x86/kernel/early_printk.c b/arch/x86/kernel/early_printk.c >> > index b9c830c..783cb25 100644 >> > --- a/arch/x86/kernel/early_printk.c >> > +++ b/arch/x86/kernel/early_printk.c >> > @@ -170,10 +170,13 @@ asmlinkage void early_printk(const char *fmt, ...) >> >     int n; >> >     va_list ap; >> > >> > -   va_start(ap, fmt); >> > -   n = vscnprintf(buf, sizeof(buf), fmt, ap); >> > -   early_console->write(early_console, buf, n); >> > -   va_end(ap); >> > +   if (early_console && (early_console_initialized || >> > +                         boot_params.screen_info.orig_video_isVGA == 1)) { >> > +           va_start(ap, fmt); >> > +           n = vscnprintf(buf, sizeof(buf), fmt, ap); >> > +           early_console->write(early_console, buf, n); >> > +           va_end(ap); >> > +   } >> >  } >> > >> >  static inline void early_console_register(struct console *con, int keep_early) >> > @@ -233,6 +236,12 @@ static int __init setup_early_printk(char *buf) >> >  #endif >> >             buf++; >> >     } >> > + >> > +   /* If there is no VGA device, don't try to use it as early console. */ >> > +   if (early_console == &early_vga_console && >> > +       boot_params.screen_info.orig_video_isVGA != 1) >> > +           early_console = NULL; >> >> Wouldn't it be better to switch to, say, serial console here to avoid >> the NULL check in early_printk()? >> > This would be another possibility. > > However, since the serial console was not explicitly selected, it would possibly > not be initialized. My understanding is that Peter had a problem with that. > > One can argue that it would still be better to select the serial console in that case, > even though it might not be initialized. Actually, most likely it is (if it exists), > since the system must presumably have some means to communicate with the world. > > I am pretty much open to either option, if that results in the patch being accepted. > Just let me know which way to go. Peter?