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    SubjectRe: [PATCH] x86/trampoline: fallback to fixed trampoline address if no e820 map is provided
    Date
    On Tuesday 14 December 2010 22:19:39 Florian Fainelli wrote:
    > From: Florian Fainelli <ffainelli@freebox.fr>
    >
    > Since 893f38d1 (x86: Use find_e820() instead of hard coded trampoline
    > address), the trampoline base address should be provided by the BIOS as an
    > e820 area. Some minimalistic BIOSes (like CEFDK on CE4100) may not provide
    > any e820 area, still we should fallback to a fixed trampoline base address
    > for SMP to work correctly.
    >
    > Cc: Dirk Brandewie <dirk.brandewie@gmail.com>
    > Cc: sodaville@linutronix.de
    > Cc: Ingo Molnar <mingo@elte.hu>
    > Cc: Yinghai Lu <yinghai@kernel.org>
    > Signed-off-by: Florian Fainelli <ffainelli@freebox.fr>

    Ingo, Yinghai, anything wrong with that patch? Thank you.

    > ---
    > diff --git a/arch/x86/include/asm/trampoline.h
    > b/arch/x86/include/asm/trampoline.h index f4500fb..908b395 100644
    > --- a/arch/x86/include/asm/trampoline.h
    > +++ b/arch/x86/include/asm/trampoline.h
    > @@ -16,6 +16,7 @@ extern unsigned long initial_code;
    > extern unsigned long initial_gs;
    >
    > #define TRAMPOLINE_SIZE roundup(trampoline_end - trampoline_data,
    > PAGE_SIZE) +#define TRAMPOLINE_BASE 0x6000
    >
    > extern unsigned long setup_trampoline(void);
    > extern void __init reserve_trampoline_memory(void);
    > diff --git a/arch/x86/kernel/trampoline.c b/arch/x86/kernel/trampoline.c
    > index f1488a3..d025aae 100644
    > --- a/arch/x86/kernel/trampoline.c
    > +++ b/arch/x86/kernel/trampoline.c
    > @@ -21,8 +21,11 @@ void __init reserve_trampoline_memory(void)
    >
    > /* Has to be in very low memory so we can execute real-mode AP code. */
    > mem = find_e820_area(0, 1<<20, TRAMPOLINE_SIZE, PAGE_SIZE);
    > - if (mem == -1L)
    > - panic("Cannot allocate trampoline\n");
    > + if (mem == -1L) {
    > + printk(KERN_INFO "BIOS did not provide e820 area for trampoline"
    > + " ,using static trampoline address\n");
    > + mem = TRAMPOLINE_BASE;
    > + }
    >
    > trampoline_base = __va(mem);
    > reserve_early(mem, mem + TRAMPOLINE_SIZE, "TRAMPOLINE");


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