Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757235AbYCDNbe (ORCPT ); Tue, 4 Mar 2008 08:31:34 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752369AbYCDNbZ (ORCPT ); Tue, 4 Mar 2008 08:31:25 -0500 Received: from out3.smtp.messagingengine.com ([66.111.4.27]:56177 "EHLO out3.smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751458AbYCDNbZ convert rfc822-to-8bit (ORCPT ); Tue, 4 Mar 2008 08:31:25 -0500 Message-Id: <1204637483.28473.1240465303@webmail.messagingengine.com> X-Sasl-Enc: 701UKV/fo+YLaPfuPmBp4IcRwAFAqfg6L3EuNungSZrt 1204637483 From: "Alexander van Heukelum" To: "Mark McLoughlin" , "H. Peter Anvin" Cc: "Ingo Molnar" , "Ian Campbell" , "Andi Kleen" , "Thomas Gleixner" , "Jeremy Fitzhardinge" , "LKML" , "Alexander van Heukelum" Content-Disposition: inline Content-Transfer-Encoding: 8BIT Content-Type: text/plain; charset="ISO-8859-1" MIME-Version: 1.0 X-Mailer: MessagingEngine.com Webmail Interface References: <47C22568.1010405@zytor.com> <1203958478.20033.1239002461@webmail.messagingengine.com> <20080225170134.GA15839@elte.hu> <20080225180750.GA31054@mailshack.com> <20080228131341.GA25213@mailshack.com> <1204232996.28798.8.camel@cthulhu.hellion.org.uk> <20080229114943.GA1909@mailshack.com> <1204305247.2037.2.camel@muff> <1204310323.24514.1239870063@webmail.messagingengine.com> <1204322819.6299.1.camel@muff> <20080301160911.GA13271@mailshack.com> <1204631082.16613.7.camel@muff> Subject: Re: [PATCH] reserve end-of-conventional-memory to 1MB on 32-bit v2 In-Reply-To: <1204631082.16613.7.camel@muff> Date: Tue, 04 Mar 2008 14:31:23 +0100 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4041 Lines: 106 On Tue, 04 Mar 2008 11:44:42 +0000, "Mark McLoughlin" said: > On Sat, 2008-03-01 at 17:09 +0100, Alexander van Heukelum wrote: > > This patch adds explicit detection of the EBDA and reservation > > of the rom and adapter address space 0xa0000-0x100000 to the > > i386 kernels. Before this patch, the EBDA size was hardcoded > > as 4Kb. Also, the reservation of the adapter range was done by > > modifying the e820 map which is now not necessary any longer, > > and that code is removed from copy_e820_map. > > > > The amount of conventional memory and the start of the EBDA are > > detected by reading the BIOS data area directly. Paravirtual > > environments do not provide this area, so we bail out early > > in that case. They will just have to set up a correct memory > > map to start with. > > > > Signed-off-by: Alexander van Heukelum > > > > --- > > > > Hi Ingo, > > > > This is the second attempt at a i386-version of the ebda > > patch. I hope that one of the Xen people will be able to > > check that this does not break their setups, but I think > > it will be fine after their patch to exclude the 0x9f000- > > 0x100000 area explicitly in their setup. > > Confirmed that with Ian's e820 map patch and your patch, Xen DomU boots > fine. Thanks for testing that! > > diff --git a/arch/x86/kernel/setup_32.c b/arch/x86/kernel/setup_32.c > > index a1d7071..20e537b 100644 > > --- a/arch/x86/kernel/setup_32.c > > +++ b/arch/x86/kernel/setup_32.c > > @@ -385,15 +385,60 @@ unsigned long __init find_max_low_pfn(void) > > return max_low_pfn; > > } > > > > +#define BIOS_EBDA_SEGMENT 0x40E > > +#define BIOS_LOWMEM_KILOBYTES 0x413 > > + > > /* > > - * workaround for Dell systems that neglect to reserve EBDA > > + * The BIOS places the EBDA/XBDA at the top of conventional > > + * memory, and usually decreases the reported amount of > > + * conventional memory (int 0x12) too. This also contains a > > + * workaround for Dell systems that neglect to reserve EBDA. > > + * The same workaround also avoids a problem with the AMD768MPX > > + * chipset: reserve a page before VGA to prevent PCI prefetch > > + * into it (errata #56). Usually the page is reserved anyways, > > + * unless you have no PS/2 mouse plugged in. > > */ > > static void __init reserve_ebda_region(void) > > { > > - unsigned int addr; > > - addr = get_bios_ebda(); > > - if (addr) > > - reserve_bootmem(addr, PAGE_SIZE, BOOTMEM_DEFAULT); > > + unsigned int lowmem, ebda_addr; > > + > > + /* To determine the position of the EBDA and the */ > > + /* end of conventional memory, we need to look at */ > > + /* the BIOS data area. In a paravirtual environment */ > > + /* that area is absent. We'll just have to assume */ > > + /* that the paravirt case can handle memory setup */ > > + /* correctly, without our help. */ > > +#ifdef CONFIG_PARAVIRT > > + if ((boot_params.hdr.version >= 0x207) && > > + (boot_params.hdr.hardware_subarch != 0)) { > > + return; > > + } > > +#endif > > This is a bit magic, is it worth splitting it out as something like > is_paravirt_environment() ? Yes, I guess it would make sense, but do we really want to start creating accessor functions to the boot_params struct? If we do, then maybe put this as an inline function in ? I don't think is the right place for this. Should is_paravirt_environment then always return 0 if CONFIG_PARAVIRT is not set? Maybe a function like get_subarch would be preferable? or has_legacy_bios_areas? I don't know. If someone makes a reasonable suggestion, I'll code it up. Greetings, Alexander > Cheers, > Mark. -- Alexander van Heukelum heukelum@fastmail.fm -- http://www.fastmail.fm - And now for something completely different? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/