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    SubjectRe: [PATCH] x86/trampoline: fallback to fixed trampoline address if no e820 map is provided

    ----- "Yinghai" <yinghai@kernel.org> a écrit :

    > On Dec 23, 2010, at 1:57 AM, Florian Fainelli <ffainelli@freebox.fr>
    > wrote:
    >
    > > 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.
    >
    > No e820 memmap ?

    Yes, the BIOS is only doing the very minimal setup to get a kernel in real-mode booting.

    >
    > Not sure how does it work
    >
    > Do you have boot log with debug ?

    I would need to produce one for you, give me a couple days to be in sync.

    >
    > Also recent kernel is using memblock already for finding free area.
    >
    > Thanks
    >
    >
    >
    > >>
    > >> 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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