Messages in this thread | | | Subject | Re: [PATCH] reserve end-of-conventional-memory to 1MB on 32-bit v2 | From | Mark McLoughlin <> | Date | Tue, 04 Mar 2008 11:44:42 +0000 |
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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.
> 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.
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