From f2d85299b7f11f73cc0a294e396cdae114e75787 Mon Sep 17 00:00:00 2001 From: "Luis R. Rodriguez" Date: Wed, 13 Apr 2016 17:04:43 -0700 Subject: x86/init: Rename EBDA code file This makes it clearer what this is. Signed-off-by: Luis R. Rodriguez Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner 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 --- arch/x86/kernel/ebda.c | 71 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 71 insertions(+) create mode 100644 arch/x86/kernel/ebda.c (limited to 'arch/x86/kernel/ebda.c') diff --git a/arch/x86/kernel/ebda.c b/arch/x86/kernel/ebda.c new file mode 100644 index 000000000000..afe65dffee80 --- /dev/null +++ b/arch/x86/kernel/ebda.c @@ -0,0 +1,71 @@ +#include +#include +#include + +#include +#include + +/* + * 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. + * + * This functions is deliberately very conservative. Losing + * memory in the bottom megabyte is rarely a problem, as long + * as we have enough memory to install the trampoline. Using + * memory that is in use by the BIOS or by some DMA device + * the BIOS didn't shut down *is* a big problem. + */ + +#define BIOS_LOWMEM_KILOBYTES 0x413 +#define LOWMEM_CAP 0x9f000U /* Absolute maximum */ +#define INSANE_CUTOFF 0x20000U /* Less than this = insane */ + +void __init reserve_ebda_region(void) +{ + 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. + */ + if (!x86_platform.legacy.ebda_search) + return; + + /* end of low (conventional) memory */ + lowmem = *(unsigned short *)__va(BIOS_LOWMEM_KILOBYTES); + lowmem <<= 10; + + /* start of EBDA area */ + ebda_addr = get_bios_ebda(); + + /* + * Note: some old Dells seem to need 4k EBDA without + * reporting so, so just consider the memory above 0x9f000 + * to be off limits (bugzilla 2990). + */ + + /* If the EBDA address is below 128K, assume it is bogus */ + if (ebda_addr < INSANE_CUTOFF) + ebda_addr = LOWMEM_CAP; + + /* If lowmem is less than 128K, assume it is bogus */ + if (lowmem < INSANE_CUTOFF) + lowmem = LOWMEM_CAP; + + /* Use the lower of the lowmem and EBDA markers as the cutoff */ + lowmem = min(lowmem, ebda_addr); + lowmem = min(lowmem, LOWMEM_CAP); /* Absolute cap */ + + /* reserve all memory between lowmem and the 1MB mark */ + memblock_reserve(lowmem, 0x100000 - lowmem); +} -- cgit v1.2.1