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f2d85299b7
This makes it clearer what this is. Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: andrew.cooper3@citrix.com Cc: andriy.shevchenko@linux.intel.com Cc: bigeasy@linutronix.de Cc: boris.ostrovsky@oracle.com Cc: david.vrabel@citrix.com Cc: ffainelli@freebox.fr Cc: george.dunlap@citrix.com Cc: glin@suse.com Cc: jgross@suse.com Cc: jlee@suse.com Cc: josh@joshtriplett.org Cc: julien.grall@linaro.org Cc: konrad.wilk@oracle.com Cc: kozerkov@parallels.com Cc: lenb@kernel.org Cc: lguest@lists.ozlabs.org Cc: linux-acpi@vger.kernel.org Cc: lv.zheng@intel.com Cc: matt@codeblueprint.co.uk Cc: mbizon@freebox.fr Cc: rjw@rjwysocki.net Cc: robert.moore@intel.com Cc: rusty@rustcorp.com.au Cc: tiwai@suse.de Cc: toshi.kani@hp.com Cc: xen-devel@lists.xensource.com Link: http://lkml.kernel.org/r/1460592286-300-14-git-send-email-mcgrof@kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
72 lines
2.2 KiB
C
72 lines
2.2 KiB
C
#include <linux/kernel.h>
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#include <linux/init.h>
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#include <linux/memblock.h>
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#include <asm/setup.h>
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#include <asm/bios_ebda.h>
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/*
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* The BIOS places the EBDA/XBDA at the top of conventional
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* memory, and usually decreases the reported amount of
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* conventional memory (int 0x12) too. This also contains a
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* workaround for Dell systems that neglect to reserve EBDA.
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* The same workaround also avoids a problem with the AMD768MPX
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* chipset: reserve a page before VGA to prevent PCI prefetch
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* into it (errata #56). Usually the page is reserved anyways,
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* unless you have no PS/2 mouse plugged in.
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*
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* This functions is deliberately very conservative. Losing
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* memory in the bottom megabyte is rarely a problem, as long
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* as we have enough memory to install the trampoline. Using
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* memory that is in use by the BIOS or by some DMA device
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* the BIOS didn't shut down *is* a big problem.
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*/
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#define BIOS_LOWMEM_KILOBYTES 0x413
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#define LOWMEM_CAP 0x9f000U /* Absolute maximum */
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#define INSANE_CUTOFF 0x20000U /* Less than this = insane */
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void __init reserve_ebda_region(void)
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{
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unsigned int lowmem, ebda_addr;
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/*
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* To determine the position of the EBDA and the
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* end of conventional memory, we need to look at
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* the BIOS data area. In a paravirtual environment
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* that area is absent. We'll just have to assume
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* that the paravirt case can handle memory setup
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* correctly, without our help.
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*/
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if (!x86_platform.legacy.ebda_search)
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return;
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/* end of low (conventional) memory */
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lowmem = *(unsigned short *)__va(BIOS_LOWMEM_KILOBYTES);
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lowmem <<= 10;
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/* start of EBDA area */
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ebda_addr = get_bios_ebda();
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/*
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* Note: some old Dells seem to need 4k EBDA without
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* reporting so, so just consider the memory above 0x9f000
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* to be off limits (bugzilla 2990).
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*/
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/* If the EBDA address is below 128K, assume it is bogus */
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if (ebda_addr < INSANE_CUTOFF)
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ebda_addr = LOWMEM_CAP;
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/* If lowmem is less than 128K, assume it is bogus */
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if (lowmem < INSANE_CUTOFF)
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lowmem = LOWMEM_CAP;
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/* Use the lower of the lowmem and EBDA markers as the cutoff */
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lowmem = min(lowmem, ebda_addr);
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lowmem = min(lowmem, LOWMEM_CAP); /* Absolute cap */
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/* reserve all memory between lowmem and the 1MB mark */
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memblock_reserve(lowmem, 0x100000 - lowmem);
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}
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