Messages in this thread Patch in this message | | | From | "Alexander van Heukelum" <> | Subject | Re: [PATCH] reserve end-of-conventional-memory to 1MB on 32-bit v2 | Date | Tue, 04 Mar 2008 14:31:23 +0100 |
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On Tue, 04 Mar 2008 11:44:42 +0000, "Mark McLoughlin" <markmc@redhat.com> 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 <heukelum@fastmail.fm> > > > > --- > > > > 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 <asm-x86/bootparam.h>? I don't think <asm-x86/paravirt.h> 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
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