Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1764117AbYCDLrk (ORCPT ); Tue, 4 Mar 2008 06:47:40 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756894AbYCDLrb (ORCPT ); Tue, 4 Mar 2008 06:47:31 -0500 Received: from mx1.redhat.com ([66.187.233.31]:35511 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756626AbYCDLr3 (ORCPT ); Tue, 4 Mar 2008 06:47:29 -0500 Subject: Re: [PATCH] reserve end-of-conventional-memory to 1MB on 32-bit v2 From: Mark McLoughlin Reply-To: Mark McLoughlin To: Alexander van Heukelum Cc: Ingo Molnar , Ian Campbell , Alexander van Heukelum , "H. Peter Anvin" , Andi Kleen , Thomas Gleixner , Jeremy Fitzhardinge , LKML In-Reply-To: <20080301160911.GA13271@mailshack.com> 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> Content-Type: text/plain Date: Tue, 04 Mar 2008 11:44:42 +0000 Message-Id: <1204631082.16613.7.camel@muff> Mime-Version: 1.0 X-Mailer: Evolution 2.12.3 (2.12.3-1.fc8) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3132 Lines: 83 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. > 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() ? Cheers, Mark. -- 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/