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a2c606d53a
This prevents allocation of the last 2MB before 4GB. The experiment described here shows Windows 7 ignoring the last 1MB: https://bugzilla.kernel.org/show_bug.cgi?id=23542#c27 This patch ignores the top 2MB instead of just 1MB because H. Peter Anvin says "There will be ROM at the top of the 32-bit address space; it's a fact of the architecture, and on at least older systems it was common to have a shadow 1 MiB below." Acked-by: H. Peter Anvin <hpa@zytor.com> Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com> Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
49 lines
1.0 KiB
C
49 lines
1.0 KiB
C
#include <linux/ioport.h>
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#include <asm/e820.h>
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static void resource_clip(struct resource *res, resource_size_t start,
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resource_size_t end)
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{
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resource_size_t low = 0, high = 0;
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if (res->end < start || res->start > end)
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return; /* no conflict */
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if (res->start < start)
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low = start - res->start;
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if (res->end > end)
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high = res->end - end;
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/* Keep the area above or below the conflict, whichever is larger */
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if (low > high)
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res->end = start - 1;
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else
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res->start = end + 1;
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}
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static void remove_e820_regions(struct resource *avail)
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{
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int i;
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struct e820entry *entry;
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for (i = 0; i < e820.nr_map; i++) {
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entry = &e820.map[i];
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resource_clip(avail, entry->addr,
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entry->addr + entry->size - 1);
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}
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}
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void arch_remove_reservations(struct resource *avail)
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{
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/* Trim out BIOS areas (low 1MB and high 2MB) and E820 regions */
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if (avail->flags & IORESOURCE_MEM) {
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if (avail->start < BIOS_END)
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avail->start = BIOS_END;
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resource_clip(avail, BIOS_ROM_BASE, BIOS_ROM_END);
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remove_e820_regions(avail);
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}
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}
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